Reference cited in this section

9. W. Rausch, The Phosphating of Metals, ASM International and Finishing Publications Ltd., 1990, p 355-374 Safety Precautions

Safety precautions on a phosphating line must begin with the basic design of the equipment involved.

Immersion Phosphating. Proper ventilation of immersion tanks is necessary to eliminate concentration of vapors from the tanks in buildings or work areas. Local regulations in some areas, however, may prohibit exhausting directly to the outside, and special filtering equipment may be required. Tanks containing acid must be resistant to the acid they hold to eliminate the possibility of the acid corroding through the tanks and spilling on to the floor. Curbing should surround tanks to retain spilled or leaked solutions.

Spray Phosphating. Equipment used in spray phosphating must be properly vented for removing vapors. A heavy grating should surmount each of the various tanks for protecting the personnel cleaning and repairing tanks, risers, and spray nozzles. These gratings also prevent workpieces from falling into tanks from conveyors. Access doors in drain areas, which are used for checking carryover and condition of work, and for access during breakdown, should be easily opened from the inside.

Handling of Alkalis and Acids. All alkaline cleaners should be handled with care. Rubber gloves and face or eye shields should be worn when these materials are added to cleaning tanks. Should these materials contact the skin, it should be flushed with water as soon as possible. Repeated or prolonged contact can cause skin irritation.

These precautions apply also to handling the phosphoric acid and chromic acid used in phosphating. Although chromic acid is oxidizing, it does not burn the skin immediately, as do common mineral acids, but severe irritation results from prolonged exposure to the skin. Goggles or face shields should be worn at all times during handling of chromic acid, because contact with the eyes can cause serious damage. All contaminated clothing should be removed and washed before reuse.

To transfer liquid from a carboy, a carboy-tilter, commercial siphon, or bulb siphon should be used. Liquid should never be drawn from a carboy by using air pressure to force it out, even when using the so-called air pressure reducers. Danger is always present that the carboy will break, or even explode, and spray or splash acid on the operator. This also holds true for drums. All drums should be specified to be plugged with one-way breather plugs. If this is not possible, the solid plug must be removed carefully to avoid acid spray, and only enough to permit the compressed gases to escape slowly. Once the inside and outside pressures are equalized, the plug may be removed.

Cyanide (Ref 10, 11) is a highly toxic chemical that can kill almost instantly. Nevertheless, despite the constant and widespread use of cyanide, deaths and illnesses associated with its use are rare. There is little danger if certain guidelines are followed closely:

• All containers for cyanide, full or empty, should have airtight lids, be stored in a well-ventilated area, and be clearly labeled as containing poison. No unauthorized person should have access to them.

• Cyanide should be handled only with gloved hands or tongs, in a well-ventilated area.

• Keep work areas meticulously clean. Spills of acid and cyanide that combine on the shop floor, or in floor drains, can generate hydrogen cyanide gas. The gas is extremely lethal if inhaled; it is the primary cause of cyanide-related deaths.

• Be prepared to provide immediate first aid in case of contact with cyanide salts. Wash the affected area in water, then with dilute sodium hypochlorite or bleaching powder solution, when with water again.

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