7A Prange in Spectrochim Acta Vol 44B 1989 p 437

Tromp, and M.C. Reuter, in Thin Solid Films, No. 236, 1993, p 140 Electron Spectroscopies (AES and XPS) AES and XPS determine the energies of electrons emitted from a surface. Those with specific energies usually are photoelectrons or Auger electrons. For detailed information, the reader is referred to Ref 3, 5, and 6. Principles for basic understanding are briefly characterized in the following and illustrated by some examples. X-ray Photoelectron Spectroscopy....

Salt Bath Descaling

The removal of oxide scale can be accelerated by using baths of molten sodium hydroxide (NaOH) to which certain reagents are added. These baths can be used with virtually all grades of stainless steel. Salt bath descaling has several advantages It acts only on the scale and does not result in metal loss or etching. It does not preferentially attack areas in which intergranular carbides are present. It is particularly useful in descaling the straight chromium grades without the preliminary...

Hot Dip Galvanizing

Hot dip galvanizing is a process in which an adherent, protective coating of zinc and iron-zinc alloys is developed on the surfaces of iron and steel products by immersing them in a bath of molten zinc. Most zinc coated steel is processed by hot dip galvanizing. In general, steels with the following maximum alloying impurity levels are best suited to galvanizing 0.05 Si, 0.05 P, 0.25 C, and 1.3 Mn. Batch Galvanizing. One method of hot dip galvanizing is the batch process, which is used for...

Eq

Where T T(z, t) is the temperature of the workpiece, t is time, and R is the fraction of the generated heat that flows into the workpiece. The solution to this boundary value problem is (Ref 17) where erfc is the complementary error function. On the surface Assuming that at a particular point on the surface the heat is applied beginning at x -a, the time of heating for a point on the surface is t (a - x)IV and the temperature at a point on the surface is The form of this analysis is consistent...

Chromating Mechanism

Next to the alkali metals, the metals that chromate coatings must protect against corrosion (i.e., aluminum, magnesium, zinc, and cadmium) are the most active metals in the periodic table. In fact, from the large negative standard electrode reduction potentials for aluminum and magnesium dissolution, one would expect these metals to dissolve when immersed in water. This does not occur, of course upon exposure to water or air, these metals immediately form a hydrated oxide film that is itself...

Methods of Application

Rust-preventive compounds are applied by Spraying or fogging electrostatically The type of rust preventive and the quantity, size, complexity, and surface finish of the articles to be coated will determine which method should be used. The equipment and methods of application are similar to those used in painting. Petrolatum compounds can be applied either hot or cold. Generally, cold application is restricted to parts that are either too large and bulky for practical tank immersion or require...

Powder Coating

Powder coatings are paint films that are applied to parts as a dry powder. The powders are basically the same type of polymers and resins (see Table 1) as used in liquid coatings except no solvent is used. Instead, the coating composition is ground to a fine powder. After application the film is formed by fusing the powder particles at temperatures above the melting point of the powder. Powder coatings are used on a wide range of products including metal furniture, wire goods such as baskets...

Types of Electroless Alloy Plating Systems

Most electroless alloy systems are based on nickel alloys and have been developed from basic electroless nickel-plating technology. Many alloy systems are documented in the literature and several are commercially available. In the following section each coating type is summarized and its availability is indicated as either production or laboratory. Nickel-Phosphorus. Electroless nickel-phosphorus is the most common nonelectrolytic alloy coating system. Electroless nickel has been used since the...

Cadmium Plating

Cadmium is primarily plated from a cyanide electrolyte. Acid cadmium baths are also used to a limited extent, and are fluoborate, sulfate, or chloride in nature. The acid-type baths are more desirable if hydrogen embrittlement is a problem, and their waste treatment is simplified. However, the cyanide baths are easier to control than the acid baths. Typical cadmium plating compositions are described in the article Cadmium Plating in this Volume. Applications and Properties....

Zn55Al Alloy Coatings

The purpose of Zn-55Al alloy coatings is to combine the excellent long-term atmospheric corrosion resistance of aluminum with the sacrificial characteristics of galvanized in a single coating (Ref 23, 24). Long-term studies showed that the 55 Al alloy was the optimum composition of the aluminum-zinc system. Steel sheet coated with this alloy was first produced commercially in 1972 in the United States under the trademark Galvalume. Coating thicknesses are usually in the range of 20 to 25 pm...

Problems and Corrective Procedures

Faulty operation of a chromium-plating solution can result in slow plating speed or deposits with undesirable characteristics. The problems encountered in hard chromium plating are similar for all three chemistries. Possible causes and suggested corrective procedures include Low ratio of chromic acid content to total catalyst content. Correct by adding chromic acid or by precipitating sulfate, if too high, with barium carbonate. Passive or scaled anodes. Correct by cleaning and reactivating...

Surface Hardening

Surface hardening is used to extend the versatility of certain steels by producing combinations of properties not readily attainable in other ways. For many applications, wear and the most severe stresses act only on the surface of a part. Therefore, the part may be fabricated from a formable low- or medium-carbon steel, and is surface hardened by a final heat treatment after all other processing has been accomplished. Surface hardening also reduces distortion and eliminates cracking that might...

Plating in High Efficiency Sodium and Potassium Cyanide Baths

High-efficiency sodium and potassium cyanide baths allow the use of higher current densities. Cyanide plating baths typically decrease in cathode efficiency, or speed of deposition, with increasing current, which accounts for the good plate distribution (throwing power). The cathode efficiency approaches 100 only at low current densities, often 10A dm2 or less. With more practical current densities of 2.0 to 3.0 A dm2, the cathode efficiency may drop 20 , especially with lower agitation rates....

High Precision Fixed Abrasive Finishing

A variety of high-precision processes have been in use, and new processes are constantly being developed to achieve extremely close geometric tolerances or to improve surface finish. The objective of all high-precision processes is to achieve geometrically precise components or surfaces of controlled texture or surface finish (Fig. 11). Table 5 compares the processes described in this section. A parallel set of processes using loose abrasives, called lapping, buffing, and polishing, are...

Group IIIV Semiconductor Growth Parameters

Group III-V semiconductors are the major materials used in optoelectronic and high-frequency electronic device applications. The ability to tailor the band structure and lattice constant in ternary and quaternary alloys by varying the composition represents one of the desirable features of these materials. The GaAs-based materials described below include not only GaAs, but gallium indium phosphide (GaInP), gallium aluminum arsenide (GaAlAs), and gallium indium arsenide phosphide (GaInAsP). GaAs...

Metallurgical Factors

A wide variety of metallurgical effects can occur during a finishing process formation of untempered or overtempered martensite, retained austenite, volume changes due to phase transformation, oxidation, and other effects can become important, depending on the mechanical and thermal aspects of the finishing operation. Reference 9 provides a good introduction to these phenomena in the case of grinding, while Ref 1 reviews various metallurgical alterations in the cases of milling, reaming,...

13DB Chrisey and GK Hubler Pulsed Laser Deposition of Thin Films Wiley 1994 General Description

In PVD of multicomponent thin films, the preparation of a stoichiometric vapor is often difficult to achieve. When singleelement sources are used, the arrival rate of each individual component must be calibrated and inter-regulated. In PLD, the composition of the vapor is the same as that of the target. Starting with the correct composition of the vapor greatly facilitates the growth of a desired phase in the depositing film. In addition, the absence of filaments or charged particles allows...

Organic Coatings

Paint is applied to a steel sheet or a part for one or both of the following reasons enhancement of the aesthetic value of the product and or preservation of structural integrity. The former goal is a consideration for the designer and will receive no further discussion in this section. The latter goal, however, will be discussed as it applies to prepainted steel. This section will describe how paints deter corrosion, the prepainting process, the primary differences between prepaint paint...

Anodizing Processes

The three principal types of anodizing processes are chromic processes, in which the electrolyte is chromic acid sulfuric processes, in which the electrolyte is sulfuric acid and hard anodic processes that use sulfuric acid alone or with additives. Other processes, used less frequently or for special purposes, use sulfuric acid with oxalic acid, phosphoric acid, oxalic acid, boric acid, sulfosalicylic acid, sulfophthalic acid, or tartaric acid. Except for thicker coatings produced by hard...

Nickel Anode Materials

Most nickel plating processes are operated with soluble nickel anode materials. Nickel from the anode is converted into ions that enter the plating solution to replace those discharged at the cathode. In addition, the anode distributes current to the parts being plated and influences metal distribution. The simplest way to satisfy anode requirements is to suspend nickel bars from hooks placed on an anode bar so that the nickel, not the hook, is immersed in the plating solution. Nickel anode...

Characteristics of Copper Plate

Variations in processing during surface preparation or during plating have significant effects on the quality of the copper electrodeposit. Certain variations can adversely affect the adhesion of copper to the substrate metal. Variations also can affect brightness, porosity, blistering, roughness, hardness, solderability, and leveling. Brightness. Bright copper coatings are generally obtained by the addition of brighteners to the electrolyte, although buffing of the electrodeposited coating...

Spindle Finishing Machines

Spindle finishing is categorized as a mass finishing process, although parts to be deburred or finished are mounted on fixtures. The process uses fine abrasive media for finishing. The spindle machine is a circular rotating tub that holds the abrasive media, and a rotating or oscillating spindle to which the part is fixed. The workpiece mounted on the spindle is immersed into the rapidly moving abrasive slurry, causing the abrasive to flow swiftly over rough edges and over the surfaces of...

Zinc Coatings

Hot-dip-zinc-coated steel sheet, also called galvanized, is by far the most widely used coated sheet product. About 86 of the hot-dip-coated sheet produced in the United States (see Fig. 1) is zinc coated. As evident in Table 1, hot dip zinc coatings for sheet are available in a broad range of coating thicknesses. For generalpurpose galvanized sheet, 19 pm (0.75 mil) per side is the usual thickness. This corresponds to a two-side coating mass of 275 g m2 (0.9 oz ft2). Heavier coatings are used...

Vapor Degreasing Equipment

All vapor degreaser designs provide for an inventory of solvent, a heating system to boil the solvent, and a condenser system to prevent loss of solvent vapors and control the upper level of the vapor zone within the equipment. Heating the degreaser is usually accomplished by steam. However, electrical resistance (< 3.0 W cm2 or < 20 W in.2) heaters, gas combustion tubes, and hot water can be used. Gas combustion heaters with open flames located below the vapor degreaser are not recommended...

Enameling Furnaces

Fusing of the porcelain enamel coating to its metal substrate or to a ground coat can be done in a continuous, intermittent, or batch furnace. The furnace may be heated by oil, natural gas, propane gas, or electricity. With oil heating, a muffle furnace is required to prevent the products of combustion from contaminating the enamel coating. Gas-fired furnaces are either muffle or radiant-tube, with a limited number of luminous-wall, direct-fired furnaces being used. Continuous furnaces are of...

Electrodischarge Machining

Electrodischarge machining (EDM) is a thermoelectric process that removes material from the workpiece by a series of discrete sparks between a work and tool electrode immersed in a liquid dielectric medium. The method of removal of material from the workpiece is by melting and vaporizing minute amounts of electrode material, which are then ejected and flushed away by the dielectric (Ref 1, 14). The two major types of EDM are die sinking EDM and wire EDM (WEDM). Die sinking EDM is traditionally...

13R Weil and K Sheppard Mater Char Vol 28 1992 p 103112

Bull, Surf Coat. Technol, Vol 39 40, 1989, p 315 Experimental Techniques for Microstructural Characterization It is not possible to determine all the structural features of a material using any one analysis technique. Therefore, many techniques that can be used to provide information about specific microstructural features have been developed. It is important to know what factors are important in any application before undertaking a program of structural analysis. For...

Process Capabilities

The thickness of mechanical plating deposits ranges from 5 to 75 pm (0.2 to 3 mils). The heavier coatings are referred to as mechanical galvanizing or cold-impact galvanizing coatings. Because the coating thickness is somewhat independent of cycle time and is controlled by the plating metal additions, a heavy galvanized coating thickness can be applied in almost as little time as thinner commercial coating thicknesses. Mechanical galvanizing provides uniform, smooth, and...

Hexavalent Chromium Plating

The first hexavalent chromium plating bath used for decorative plating, sometimes referred to as the conventional bath, consisted of an aqueous solution of chromic anhydride (CrO3) and a small amount of soluble sulfate (SO4 ), referred to as the catalyst. The latter was added as sulfuric acid or as a soluble sulfate salt, such as sodium sulfate. When dissolved in water, the chromic anhydride forms chromic acid, which is believed to exist in the following equilibrium The ratio of chromic acid to...

Introduction

METALLURGICALLY CLEAN SURFACES are necessary to promote the proper bonding of continuously applied dip, barrier, and chemical conversion coatings on steel substrates. Surface preparation removes contaminants on the substrate that would prevent the optimal metallurgical bonding of the coating. There are two basic types of contaminants. Carbonaceous materials, which include oils, represent one type. These materials are actually applied to the steel strip during the cold-reduction process to...

Advantages of Organic Acids

Although organic acids are relatively weak, they remove metal oxides through the following mechanisms. As the organic acid reacts with the metal to produce citrates, acetates and other byproducts, hydrogen gas is released. The hydrogen builds up under the scale and can often lift the remaining oxides off the metal. In addition, organic acids act as sequesterants by tying up the dissolved metal ions and carrying them away from the surface being cleaned. With the use of heated solutions and...

References cited in this section

Mattox, Particle Bombardment Effects on Thin-Film Deposition A Review, J. Vac. Sci. Technol. A, Vol 7 (No. 3), 1989, p 1105 15. J.M.E. Harper, J.J. Cuomo, R.J. Gambino, and H.R. Kaufman, Modification of Thin Film Properties by Ion Bombardment during Deposition, Chapter 4, Ion Bombardment Modification of Surfaces Fundamentals and Applications, O. Aucello and R. Kelly, Elsevier, 1984 16. D.M. Mattox, Adhesion and Surface Preparation, Chapter 3, Deposition Technologies for Films and...

CH3SiCl3 SiC 3HCl

The reaction temperature ranges from 900 to 1400 C (1650 to 2550 F), and pressure ranges from 1.3 to 6.7 kPa (10 to 50 torr) in a hydrogen atmosphere. The deposition rate and the crystallite size increase with the increasing partial pressure of MTS. Other precursor combinations are SiCl4 CH4, SiCl4 CCl4, SiH2Cl2 C3H8, and SiHCl3 C3H8, usually in a hydrogen atmosphere. Titanium carbide (Ref 33) is of major industrial importance in the coating of wear-resistant tools by the CVD process. The most...

4Techni Solder NF 1957 product data sheet Technic Inc Cranston RI Fluoborate Plating Solutions for Tin Lead

Any desired tin-lead alloy composition can be plated from a fluoborate solution. The composition of the deposit depends on the amount of stannous tin and lead in the solution, the type and amount of addition agent, the current density, and the tin-lead content of the anodes. Bath temperature and degree of agitation also affect the composition, especially in highspeed solutions. Solution Components. Concentrated solutions of stannous and lead fluoborates and fluoboric acid are available...

Surface Hardening of Ductile Iron

Ductile iron responds readily to surface hardening by flame, induction, or laser heating, or by nitriding. Because of the short heating cycle in these processes, the pearlitic types of ductile iron ASTM 80-60-03 and 100-70-03 are preferred. Irons without free ferrite in their microstructure respond almost instantly to flame or induction heating and require very little holding time at the austenitizing temperature in order to be fully hardened. With a moderate amount of free ferrite, the...

Cyanide Zinc Baths

Bright cyanide zinc baths may be divided into four broad classifications based on their cyanide content regular cyanide zinc baths, midcyanide or half-strength cyanide baths, low-cyanide baths, and microcyanide zinc baths. Table 1 gives the general composition and operating conditions for these systems. Table 1 Composition and operating conditions of cyanide zinc baths Table 1 Composition and operating conditions of cyanide zinc baths Mid or half-strength cyanide bath(b) Note Cathode current...

Vaporization Sources

Common heating techniques for evaporation sublimation include resistive heating, high-energy electron beams, low-energy electron beams, and inductive (radio frequency) heating. Figures 7, 8(a), and 8(b) show some vaporization source configurations. Resistive heating is the most common technique for vaporizing materialat temperatures below about 1800 C (3270 F), while focused electron beams are most commonly used above 1800 C (3270 F). Fig. 7 Sources used for resistive heating of materials in...

Flame Cleaning and Furnace Preparation

Sendzimir Oxidation Reduction Method. The original method for flame cleaning was proposed by Tadeusz Sendzimir in the 1930s. His invention involved heating a steel strip in a direct oxidizing flame to burn off the rolling oils and other contaminants. This step left an oxide on the steel surface, which was then cleaned by heating to a much higher temperature in a reducing furnace with a hydrogen-nitrogen atmosphere. This two-furnace cleaning method was converted into a coating line by cooling...

Spraying

Spraying is adaptable to either large-volume or low-volume production. Applications may be limited because of solvent emissions, possible fire hazards, or potential damage from overspray. Spraying methods include conventional air spraying, in which the paint is atomized and propelled against the work by means of compressed air, hot spraying, hydraulic airless spraying, and air and airless electrostatic spraying. Spraying is used for applications in which good appearance and uniformity of...

Sources of Depositing Species

The various thermal vaporization sources can be used in ion plating. For plasma-based ion plating, the resistively heated sources are most often used. Low-energy electron-beam heating from hollow cathode sources and thermionic sources can be used, often with a magnetic confining field. This allows the electrons to heat the material to be vaporized and also to create the plasma. High-energy electron-beam heating can be used, but this requires isolating the electron-emitting...

Removal of Residues from Magnetic Particle and Fluorescent Penetrant Inspection

Successful removal of the iron oxide particles deposited on ferrous parts during magnetic particle inspection requires complete demagnetization of the part. After demagnetization, emulsion cleaning is an effective and practical means of removing both the iron oxide residues and oil. Fluorescent pigments used for similar inspection of aluminum parts can be removed with hot alkaline cleaners. For low-to-moderate production, an efficient procedure consists of immersing parts in a light, undiluted,...

16JR Treglio AJ Perry and RJ Stinner Surface and Coatings Technology Vol 65 1994 p 184 Applications

Table 2 outlines some of the research and development applications that have been pursued using directed beam ion implantation technology. Of the properties listed, the tribological aspects of ion implantation have received the most attention (Ref 17). In spite of the relatively shallow penetration of implanted ions (typically nitrogen), implanted surfaces have often demonstrated a high degree of resistance to wear under mild abrasive or lubricated sliding conditions. This wear resistance is...

4HF H3BO3 HBF43H2OEq 6

Where HBF4is the resultant fluoboric acid. The reaction is reversible if the stoicheiometric amount of boric acid (H3BO3)is used to react with the hydrofluoric acid (HF) present. As the amount of boric acid in the above reaction is increased, the reaction is driven far to the right so that the reaction becomes irreversible and no free hydrofluoric acid is regenerated. This is important because if free hydrofluoric acid were present, then insoluble fluorides, especially lead fluoride, would...

Thermal Spray Coatings

Thermal spray coatings are surface coatings engineered to provide original equipment with resistance to wear, erosion, abrasion, corrosion, and oxidation. Thermal spraying is also used to repair and upgrade in-service equipment. In general, thermal spray coatings can be applied to a range of substrate materials, including metals, ceramics, plastics, and polymer composites. Such coatings often are used instead of paint because of their predictable service life, increased effectiveness, and lower...

Growth of Nuclei

When atoms condense they form nuclei. If the surface is of the same material as the depositing atoms, the process is called homogeneous nucleation if they are of different materials, the process is call heterogeneous nucleation. In semiconductor terminology, heterogeneous nucleation forms heterojunctions. Three types of nucleation mechanisms have been identified they differ according to nature of interaction between the deposited atoms and the substrate material (Ref 23) (a) the van der Merwe...

Hydrogen Embrittlement

If an electrodeposited coating is to be applied to a highly stressed part or a high-strength (over 1100 MPa, or 160 ksi) heat-treated steel part, it is important that the processing not decrease the static or fatigue strength of the part. Hydrogen embrittlement does not affect fatigue life. Coatings having high residual stresses, such as chromium, affect fatigue life however, this is not the case with cadmium. Cadmium deposited from a cyanide solution is more likely to produce hydrogen...

ECM Equipment

Figure 2 shows a schematic representation of the ECM system for finishing of a die or other complex shapes. The major components include the workpiece, cathode tool, electrolyte, power supply, and electrolyte circulating and purification system. A low voltage (8 to 30 V) is normally applied across the electrodes. A small gap (0.2 to 1 mm) is maintained between them, producing a current density of the order of 10 to 100 A cm2 (Ref 1, 2, 3). The electrolyte is forced through the small gap between...

Operating Parameters of Standard Cyanide and Midcyanide Zinc Solutions

Almost every physical form of zinc anode material has been used in cyanide zinc plating, the type and prevalence varying from country to country. In the United States, cast zinc balls approximately 50 mm (2 in.) in diameter, contained in spiral steel wire cages, are by far the most common anode material. A practical variation of this is the so-called flat top anode, with a flat surface to distinguish it from cadmium ball anodes. The use of ball anodes provides maximum anode area, ease...

Carburizing Boriding and Flame Hardening

Carburizing is a case-hardening process in which carbon is dissolved in the surface layers of a steel part at a temperature sufficient to render the material austenitic, followed by quenching and tempering to form a martensitic microstructure. The resulting gradient in carbon content below the surface of the part causes a gradient in hardness, producing a strong, wear-resistant surface layer. In gas carburizing, commercially the most important variant of carburizing, the source of carbon is a...

Grinding

A wide variety of abrasive finishing processes termed grinding are practiced in the finishing of industrial components. They offer the following advantages (compared to machining processes that use defined cutting edges) The range of surface geometries generated (e.g., contours, profiles, etc.) is frequently more complex than is economically possible in single-point machining processes. Grinding wheels can be used for high stock removal (i.e., rough grinding). The same wheel is often modified...

Surface Preparation

To ensure adequate bonding of thermal spray coatings, it is critical that a substrate be properly prepared. Surfaces must be clean, and usually substrates must be roughened after cleaning by grit blasting or some other means. Of course, the surface must remain uncontaminated by lubricants from handling equipment or body oils from hands and arms after it is prepared. It is recommended that the prepared surface be coated as soon as possible after preparation to prevent the possibility of...

Environmental Impact

Most cleaning salts are formulated from alkali metal salts, as previously described. Some of these ingredients may be highly alkaline and corrosive. Process chemicals formulated for salt bath cleaning applications do not contain restricted or heavy metals in their fresh condition. The byproducts or sludge that must be removed from an operating bath will contain the materials that were processed in it. For example, byproducts formed from paint stripping applications will contain heavy metals if...

Curtain Coating

Gravity Changing Machine

Curtain coating is a method of applying finishes at high speeds with little paint loss. In curtain coating, flat or shaped strip and sheet are moved by conveyor belt beneath a pump-fed reservoir with an adjustable slot opening at its lower edge. The slot opening provides a controlled continuous wet curtain of coating flowing onto the work. Some curtain coaters have heads that function by use of gravity overflow of material over one side of the reservoir. The pressure-fed curtain coater applies...

Plating in Pyrophosphate Baths

Copper pyrophosphate plating baths offer a number of desirable features. Copper pyrophosphate forms a highly soluble and conductive complex when dissolved in potassium pyrophosphate solution. Potassium salts are preferred because of their higher solubilities. Copper pyrophosphate plating baths operate at nearly 100 cathode efficiency and provide good throwing power. They are noncorrosive because the operating pH is near neutral. Concentration limits and operating conditions for copper...

Control of Crystal Size

The crystalline structure of the chemically bonded phosphate coating (Fig. 11) provides a suitable base for subsequent paint or oil films. Crystals permit the paint to penetrate, providing the paint with exceptional adherence. When oil is the rust preventive, the interstices of the crystalline structure function efficiently as an oil-retaining reservoir. The adhesion of phosphate coating to the base metal, as determined by flexing of the metal, varies with the type and thickness of the coating....

Application Of Electroplating In Civil Engineering

CONTINUOUS ELECTRODEPOSITION involves electroplating a pure metal or alloy coating onto an endless steel strip. In practice, this is achieved by unwinding a coil of strip welding it to the tail end of the preceding coil passing it through the sequence of surface preparation, electroplating, and surface post-treatment rewinding it and then again cutting it from the preceding coil. The facilities used for this process are commonly called continuous plating lines and can handle strip of up to...

Equipment

The equipment used in shot peening is essentially the same as that used in abrasive blast cleaning, except for certain auxiliary equipment made necessary by the more stringent controls imposed in the shot peening process. For a description of basic equipment, such as cabinets, wheels, nozzles, and conveyors, see the article Mechanical Cleaning Systems in this Volume. The principal components of shot peening equipment are a shot-propelling device, shot recycling and classification arrangements,...

Acid Descaling Pickling

Acid descaling, or pickling, is the removal of heavy, tightly adherent oxide films resulting from hot-forming operations, thermal treatments (such as annealing or hardening), or welding (Ref 4). Because most stainless steel products received from the producing mill have been pickled, descaling is required only as a result of subsequent manufacturing operations. In evaluating the different methods for removing scale, it should be kept in mind that scale on stainless steel is far more complex...

Crack Patterns and Other Characteristics of Hard Chromium Plate

The quality of hard chromium plate is evaluated chiefly from the standpoint of thickness and thickness distribution, appearance, crack pattern, crack size, porosity, roughness, and adhesion of the plate to the base metal. Surface Cracks. During the deposition of chromium deposits, microcracks form to relieve the internal stress. These cracks subsequently fill in with plated chromium. The chromium in these former cracks is more easily etched and has a different refractive index than the...

Phosphate Coating

Phosphate coating is the treatment of bare or galvanized steel with a dilute solution of phosphoric acid and other chemicals in which the surface of the metal, reacting chemically with the phosphoric acid medium, is converted to an integral, mildly protective layer of insoluble crystalline phosphate. Phosphate conversion coatings are applied to steel substrates to enhance corrosion resistance, increase paint adhesion, or both. Phosphate coatings range in thickness from less than 3 to 50 pm (0.1...

Racks and Fixtures

The following recommendations are offered regarding the design and use of plating racks Racks should be designed to hold workpieces in a favorable position for plating uniformly on significant surfaces and to facilitate racking and unracking. Workpieces with protruding sections should be racked so that parts shield each other. If this is not possible, a current thief should be used to reduce current density at the protruding points. Electrical contact with the part should be made on an...

Anodizing Equipment and Process Control

Low-carbon steel tanks are satisfactory for chromic acid baths. It is common practice to line up to half of the tank with an insulating material, such as glass, to limit the cathode area with respect to the expected anode area (a 1-to-1 ratio is normal). The cathode area need only be 5 of the maximum anode area. In nonconducting tanks, suitable cathode area is provided by the immersion of individual lead cathodes however, these require the installation of additional...

Quality Control of Nickel Plating

Achieving high quality involves controlling the bath composition, the purity of the plating solution, and the thickness and uniformity of the deposits. Eliminating rejects, troubleshooting, and the testing of deposits are important aspects of process and product control. Control of Solution Composition. Control of the composition of the plating bath is one of the most important factors contributing to the quality of nickel deposits. At the outset, the bath must be prepared to the specified...

Reference cited in this section

Modification and Repair for Printed Boards and Assemblies, Manual IPC-R700B, Institute for Interconnecting and Packaging Electronic Circuits Health and Safety Considerations There are two safety issues in selective plating the chemicals and the equipment used to apply the chemicals. Overall, the process meets the safety requirements set by the Occupational Safety and Health Administration (OSHA) for in-plant use. Electrical protection of the power pack, workpiece, and operator are provided by a...

Calculating Coating Coverage and Costs

The cost of the applied coating is directly related to the cost per gallon of coating material, the application efficiency, the required thickness of film, and the spreading rate. To calculate the gallons needed and cost for coating an object the following information is needed. Volume of solids in coating Spreading rate of coating at application viscosity Dry film thickness required Volume solids content of the coating is the volume percentage of vehicle solids and pigments in a gallon of...

Anodes

Lead of satisfactory purity for anodes may be obtained either as corroding lead or chemical lead. Chemical lead anodes generally are preferred. Impurities in the anodes such as antimony, bismuth, copper, and silver cause the formation of anode slime or sludge and can cause rough deposits if they enter the plating solution. These impurities can also cause anode polarization if present in the anode, especially at higher anode current densities. Small amount of tin and zinc are not harmful. Anode...

Zinc Cobalt Plating

Zinc-cobalt coatings contain 0.6 to 2 Co. Zinc-cobalt alloys find extensive use for relatively inexpensive components in applications that require improved abrasion resistance and corrosion protection. Typically, an 8 pm film with 1 cobalt will last up to 500 h in a neutral salt spray test before red rust if the proper chromate is applied. Some reduction in corrosion resistance is experienced after exposure to high temperature, but not as much as with zinc-iron alloys. A unique attribute of...

Example 1 Residual Stresses in Grinding

The existence of residual stresses in a ground specimen is due to the combined action of mechanical and thermal effects. Mechanical Effect. Mechanical forces during grinding expand the surface of a sample, so that the plastically deformed surface experiences a compressive residual stress state while the elastically deformed near-surface layer is left in a state of residual tension. The elevation of temperature in the surface of the sample as a result of the cutting action causes a reduction in...

Removal of Unpigmented Oil and Grease

Common shop oils and greases, such as unpigmented drawing lubricants, rust-preventive oils, and quenching and lubricating oils, can be effectively removed by several different cleaners. Selection of the cleaning process depends on production flow as well as on the required degree of cleanness, available equipment, and cost. For example, steel parts in a clean and dry condition will rust within a few hours in a humid atmosphere. Thus, parts that are thoroughly clean and dry must go to the next...

MOCVD Starting Materials

The alkyls of Group II and III metals and the hydrides of Group V and VI elements are generally used as precursors in MOCVD. Dilute vapors of these chemicals are transported at or near room temperature to a hot zone, where pyrolysis reactions occur. For example, GaAs is formed by heating trimethylgallium, (CH3)3Ga, or triethylgallium, (C2H5)3Ga, and AsH3 over a suitable substrate, usually a single crystal of GaAs or silicon, at temperatures near 600 C (1110 F). The decomposition reactions can...

Ruthenium Plating

Ruthenium in the solid form is hard and brittle furthermore, it oxidizes rather easily. These factors limit its use, even as its low price relative to the other PGMs provides impetus for its application. Despite extensive research work on electroplating of ruthenium, it has obtained a small market share in only two areas for decorative applications such as eyeglass frames and for layers on electrical contacts used in sealed atmospheres. All ruthenium plating electrolytes are based on solutions...

Components of Continuous Steel Strip Plating Lines

Figures 6, 7, 8, and 9 show schematic diagrams of continuous steel electroplating lines for tin, chromium, and zinc coatings. Figure 9 may be consulted in the following discussion of the general features of these lines. The line in Fig. 9 is also designed for painting over the metallic coated strip, which for economic reasons may become the trend, particularly for zinc and zinc alloy coating lines whose lower speeds can allow roll coating of the organic films. Fig. 6 Schematic diagram of a...

Color Anodizing

Dyeing consists of impregnating the pores of the anodic coating, before sealing, with an organic or inorganic (e.g., ferric ammonium oxalate) coloring material. The depth of dye adsorption depends on the thickness and porosity of the anodic coating. The dyed coating is transparent, and its appearance is affected by the basic reflectivity characteristics of the aluminum. For this reason, the colors of dyed aluminum articles should not be expected to match paints, enamel, printed fabrics, or...

Dip Painting

Dip painting consists of submerging a part in paint contained in a tank, withdrawing the part, and permitting the part to drain. Parts with complex surfaces may be coated efficiently by dipping. Larger parts, produced in quantity, are racked or hung on conveyors, which carry the parts to the paint tank, automatically immerse and withdraw the parts, and carry them over drip troughs into which the excess paint runs off. Dip painting is seldom used where uniformity of paint thickness is required....

Group IV Semiconductor Growth Parameters

Silicon is the foundation of the present electronics industry. Epitaxial layers are used routinely in high-performance CMOS and bipolar technologies. Not surprisingly, the CVD process for silicon is the most mature. Germanium is another important Group IV semiconductor. Because both of these materials are grown from either chloride or hydride sources, they are categorized as CVD, rather than MOCVD, processes. Epitaxial silicon (Si) layers can be grown at atmospheric pressure in the temperature...

Kinetics and Gas Phase Transport

Thermodynamics determine the state of a closed system at equilibrium and indicate what to expect from the reactants on a surface (substrate) at a given temperature. However, the MOCVD process is not, by definition, an equilibrium process. Thermodynamics can only define certain limits for the growth process. It is not possible to use thermodynamics to predict the time required to attain equilibrium, what steps to take to achieve the lowest energy state, or the rates at which various processes...

Paint Stripping

Infrequently, parts have to be stripped and repainted. Possibly there is a problem with appearance the wrong paint or color may have been used. Tools, fixtures, and automatic spray line fixtures must be periodically cleaned of old paint buildup as well. Some paints are easier to strip than others, and some paint stripping methods are incompatible with some metals. A hot alkaline cleaning bath, which is a part of a metal process line, should not be used as a paint stripping tank. Even if the...

Fundamentals of Condensation

Thermally vaporized atoms may not condense when they impinge on a surface, but may rather be reflected or re-evaporate. Re-evaporation is a function of the surface temperature and the flux of depositing atoms. A hot surface can act as a mirror for atoms. For example, the deposition of cadmium on a steel surface having a temperature greater than 200 C (390 F) results in total re-evaporation of the cadmium. Figure 3 shows how this hot mirror effect can be used to monitor the deposition of the...

Bulk and Barrel Plating

The uniform plating thickness of electroless nickel coatings allows many parts that would have to be racked if they were finished electrolytically to be bulk plated. Because of the resulting labor savings, coatings such as chromium can sometimes be replaced with electroless nickel at a lower overall finished cost, although the chemical cost is higher. Four principal types of bulk plating are used Soldier-style racking Parts are placed so close together that complete coverage would be difficult,...

Mechanical Finishing

The term mechanical finishing encompasses the technology of edge and surface conditioning of metal and nonmetal products for both cosmetic and functional purposes. Generation of smooth and specular surfaces to improve appearance of components is an essential part of the manufacturing cycle of most manufactured products, but functional finishing is still more important. Most mechanisms will run longer and more efficiently if component surfaces and edges are smooth. If an appropriate scratch...

Propelling Abrasive Media

Abrasive blast cleaning began commercially with air or steam directed through a conduit of pipe or hose with a final nozzle to direct the impacting abrasive stream. Both pressure blast and suction blast nozzle systems require high power to generate the compressed air or pressurized steam that is used to accelerate and propel the abrasive. This requirement is due to aerodynamic inefficiencies in accelerating the spherical and angular abrasive particles, especially the higher-density ferrous...

Wet Cleaning Methods

Wet cleaning is a generic term that means aqueous solutions are used to prepare the surface of the strip. This term incorporates both alkaline and acid processes. The wet cleaning section of a coating line has a relatively low initial cost, compared with the cost of large, gas-fired furnaces, but requires a high degree of maintenance. In addition, the cost of the chemicals and of the disposal of spent chemicals results in high operating expenses. Alkaline Cleaning. In the dip operation of...

Finish Reaming

Reaming is traditionally a finishing process for a rough hole produced by a twist drill. With the modified drills discussed earlier, high-grade reamers corresponding to ISO Grade 4 or 5, instead of the traditional 6, give fine finished holes. Recent developments by a Japanese firm include the broach reamer, which rotates, and the carbide mill reamer, which can be used in a machining center or preferably a jig borer (Fig. 10). Broach reamers are available in sizes from 3 to 100 mm and carbide...

Sputtering Techniques

Since the discovery of sputtering by W.R. Grove in the mid-1800s, a number of sputter deposition techniques have been developed to deposit thin films of various materials, and much has been written about these techniques (Ref 6, 7, 8, 9, 10, 11, 30, 31). The following section provides a brief overview of several common techniques, including dc diode, rf diode, triode, magnetron, and unbalanced magnetron sputtering. Diode sputtering is the oldest sputtering technique. A dc diode plasma may be...

Disposal Issues

When the time comes to dispose of spent fluids, consideration must be given to the myriad of regulations that protect the environment and the people from improper dumping of hazardous materials. All municipalities and states have the authority to promulgate their own specific set of waste disposal regulations, and many have done so. It is important that before any waste is disposed of, the appropriate local, state, and federal regulations be consulted. This discussion, however, is limited to...

Finish Drilling

Next to turning, drilling is the most widely used machining process, accounting for about 25 of all machining operations, and as much as 60 in some small and medium industries. Despite this wide use, conventional drilling remains a rough process that generally needs to be finished by boring or reaming. The tool materials used for drills are high-speed steels, carbides, CBN, and diamonds. High-speed steel in the form of twist drills comes in all sizes and is used for rough machining. Carbide...

Removal of Pigmented Drawing Compounds

All pigmented drawing lubricants are difficult to remove from metal parts. Consequently, many plants review all aspects of press forming operations to avoid the use of pigmented compounds. Pigmented compounds most commonly used contain one or more of the following substances whiting, lithopone, mica, zinc oxide, bentonite, flour, graphite, white lead (which is highly toxic), molybdenum disulfide, animal fat, and soaplike materials. Some of these substances are more difficult to remove than...

Selection of a Paint System

To select a paint system consistent with the production and economic requirements of the product being coated, a general knowledge of coatings is necessary, including favorable and unfavorable characteristics, available forms, relative costs, and application methods. Table 1 lists some of the major resins used and their general properties. Many of the resins listed are compatible with others, and when blended, undergo changes of properties which provide performance not available with the...

Solution Control

To ensure a quality deposit and consistent plating rate, the composition of the plating solution must be kept relatively constant. This requires periodic analyses for the determination of pH, nickel content, and hypophosphite and orthophosphite concentrations, as well as careful temperature control. With modern premixed solutions, only checks of nickel content and pH are required. The frequency with which these analyses should be made depends on the quantity of work being plated and the volume...

Alkaline Cleaner Composition

Alkaline cleaners have three major types of components builders, which make up the bulk of the cleaner organic or inorganic additives, which promote better cleaning or affect the rate of metal oxide dissolution of the surface and surfactants. Builders are the alkaline salts in an alkaline cleaner. Most cleaners use a blend of different salts chosen from Orthophosphates, such as trisodium phosphate Condensed phosphates, such as sodium pyrophosphate and sodium tripolyphosphate The corresponding...

Rust Preventive Material Selection

The occurrence of rust on the surfaces of steel or other iron-base alloys is dependent on contact with moisture and oxygen. The extent of rusting is a function of the duration of this contact and of temperature. Temperature also affects the rate of rusting, which can be accelerated by the presence of chloride salts, oxides of sulfur, and other electrolytes that enter into or modify the chemical reactions involved. The composition and metallurgical characteristics of the alloy also influence the...

Alkaline Plating Baths

Alkaline cyanide copper solutions are used to plate the initial deposits (as a strike) on a variety of substrates. These baths can be easily controlled to produce thin deposits of relatively uniform thicknesses on all surfaces. They have the best macro throwing power, which describes the relative plating thickness distribution over all current densities. They also have traditionally been the most widely used strike and plating baths. However, with a greater emphasis on hazards and waste...

Steam Treating of PM Parts

Ferrous P M parts have traditionally been steam treated for improved wear resistance, corrosion resistance, and sealing capacity. Here, P M parts are heated in a specific manner under a steam atmosphere at temperatures between 510 to 595 C (950 to 1100 F) to form a layer of black iron oxide (magnetite, or ferrous-ferric oxide, FeO-Fe2O3) in the surface porosity according to the chemical reaction 3Fe + 4H2O (steam) FesO4 + 4H2(gas) (Eq 1) Steam treating cannot be described as a heat treatment...

Classification of Cast Irons

There are six basic types of cast irons and several varieties of each. The types of iron are classified as to how the excess carbon occurs in the microstructure. The correspondence between commercial and microstructural classification, as well as the final processing stage in obtaining common cast irons, is given in Table 1. Table 1 Classification of cast iron by commercial designation, microstructure, and fracture Solidification and heat treatment1 1 (a) F, ferrite P, pearlite A, austenite M,...

Variations in Plate Thickness

Variations in the thickness of hard chromium plate depend primarily on the potential field distribution. Potential field is controlled by the placement of anodes, shields, thieves, and other parts, as well as the relative position of the sides and surface of the tank. Variations in plate thickness also depend on surface preparation, control of solution conditions, and uniformity of the power source. Methods of Measuring Plate Thickness. Several methods and types of instruments are available for...

Accelerators

Complexing agents reduce the speed of deposition and can cause the plating rate to become uneconomically slow. To overcome this, organic additives, called accelerators or exultants, are often added to the plating solution in small amounts. Accelerators are thought to function by loosening the bond between hydrogen and phosphorous atoms in the hypophosphite molecule, allowing it to be more easily removed and absorbed onto the catalytic surface. Accelerators activate the hypophosphite ion and...

Growth Related Film Properties

Films deposited by PVD processes invariably have properties that differ from those of the bulk materials (Ref 63). For this reason the specific film properties should be determined for films made with controlled and reproducible materials and processes. The columnar morphology and the residual film stress developed during film growth are important to a number of the film properties and the stability of the deposited film structure, including Density mechanical deformation, electrical...

Plating Solutions

Chromic acid is the source of metal in hard chromium plating solutions. However, a chromic acid solution does not deposit chromium unless a definite amount of catalyst is present. If there is either too much or too little catalyst, no chromium metal is deposited. Catalysts that have proved successful are acid anions, the first of which to be used was sulfate. Substitution of fluoride ions present in complex acid radicals for a portion of the sulfate improves the chromium-plating operation. In...

Technology Drivers for Finishing Methods

Engineering activity is usually driven by a few driving forces. These technology drivers are generally universal and are often found to be independent of geography. The scale or magnitude of these drivers may vary, depending on the local demands for quality, economic forces, and so on. Technology drivers for finishing methods are addressed briefly in the following paragraphs. Tolerance in generic terms implies deviation from the nominal value. As it relates to finishing methods, tolerance...

Coating of PM Parts

In addition to the surfaces provided by steam treatment, P M parts are frequently coated by mechanical means, painting, or electroplating. The blue-black oxide-covered surface produced by exposure to steam is often the final finish for a variety of hardware items. It may also be used as a preliminary coating for a final finishing process, such as painting. Regardless of the method used for coating, major emphasis must be placed on initial cleaning. If liquid contaminants are allowed to remain...