Room Temperature Cleaning

Room-temperature or cold cleaners are aqueous solutions for removing soil without the aid of heat other than that resulting from pumping and circulating the solution or being transferred from the surrounding atmosphere. The operating range of such cleaners is usually from 21 to 46 °C (70 to 115 °F). For additional information, see the article "Alkaline Cleaning" in this Volume.

Cold alkaline cleaners, such as the silicate or phosphate types (orthosilicate or tetrasodium pyrophosphate), are chiefly used for cleaning where heat is not available, where heated solutions are not permitted, or when heating the parts above about 46 °C (115 °F) is not desirable. In a cold process for iron phosphating, for example, parts that have been cleaned in a heated solution and have not cooled sufficiently before entering the phosphate solution will yield an unacceptable phosphate coat. In some applications, an unheated cleaning solution is preferred in order to facilitate the checking of part dimensions at room temperature without the delay involved in cooling the parts after cleaning. This procedure is used for cam shafts, honed cylinder walls, and valve-guide holes in engine heads. One automotive plant utilizes a cold alkaline cleaner for removing soil from engine blocks in a power washer at the rate of 300 per hour. In another application, carburetor parts are cleaned at a rate of 600 to 700 per hour. Table 8 provides several detailed examples of the application of cold alkaline cleaners.

Table 8 Examples of application of room-temperature alkaline cleaners

Part

Surface from last operation

Relative amount of original soil on part

Residual soil on part after cleaning, mg

Aluminum alloy piston

Ground

Heavy, up to 0.75 g per part

0.1

Pinion gear, ferrous

Ground and lapped

Heavy

0.1

Ring gear, ferrous

Ground and lapped

Heavy

0.1

Part

Surface from last operation

Relative amount of original soil on part

Residual soil on part after cleaning, mg

Engine heads, ferrous

Fully machined

Heavy

1.5

Engine intake manifold, ferrous

Fully machined

Heavy

10

Carburetor throttle body, ferrous

Fully machined

Medium to heavy

0.5

Automatic transmission pump, ferrous

Fully machined

Medium to heavy

6

Cold cleaners may also reduce costs by using simpler equipment, eliminating the expense of energy for heating, and reducing maintenance requirements.

Cold acid cleaners, such as monosodium phosphate containing a detergent, are also available. Their chief use is for cleaning immediately before iron phosphating, where the advantage of a lower pH is significant. These acid cleaners have a pH of about 6 and thus impart a surface compatible with the iron phosphate bath, which has a pH of 4.5 to 5.5.

Some proprietary products now offer simultaneous cleaning and iron phosphating at room or low temperatures. In a few other isolated applications, cold acid cleaners perform satisfactorily, but in most instances heated solutions are much more efficient.

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