Processing Equipment

Because many of the electrolytes used in iron plating are very corrosive, it is necessary to choose the most corrosion-resistant materials for the processing equipment. This means at least a lined steel or stainless steel tank. However, considering the potential problems with liners, it is advisable to have tanks made out of polypropylene. The high temperatures of some of the baths make polyethylene a poor choice for tank construction.

Filters should be chlorinated polyvinyl chloride or polypropylene. Magnetically coupled pumps do not work well because of the high molar concentration of most of the solutions. Centrifugal pumps require seals, which do not hold up well in hot acidic solutions. In-tank pump and filter assemblies are highly recommended because any solution that leaves the tank and dries leaves a red-brown stain that can be a major problem in maintaining good housekeeping. There should be provision for regular carbon treatment. Care must be exercised to prevent the pump from aspirating air that aggravates the problem of oxidation.

Agitation can be mechanical or provided by the pump and filter. Air agitation should not be used because it will increase the oxidation of the ferrous to ferric iron that causes brittle, dark deposits.

Heaters should be Teflon-covered titanium except for those to be used in fluoroborate baths, which should be Teflon-coated stainless steel. Steam-heated tanks usually do not get enough for baths with higher temperatures, but they are acceptable for lower-temperature baths.

Anodes should be pure electrolytic iron (often called ARMCO iron) and should be bagged with glass fiber (except in fluoborate solutions) or Dynel anode bags to retain the sludge that comes from the anodes. In certain cases low-carbon steel anodes can be used, but these can cause incorporation of carbon into the deposit, which could cause the deposit to be very hard. This could be a problem if one of the required deposit characteristics is low hardness.

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