Iron Plating

What types of baths are available for iron plating?


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Q. I recently learned that iron plating is a well-documented plating process but is rarely discussed in the plating word. I need more information on this plating process. What types of baths are available for this type of plating? –J.M.

A. The iron plating bath is particularly useful for when large build-ups (50 - 100 thousands of an inch) are required. There are a number of different baths available: ferrous chloride, ferrous fluorborate, ferrous sulfamate and ferrous sulfate are common examples. Of these baths, the most common is the ferrous chloride bath. The make up and operation of this bath is as follows:

Component

Concentration & Operating Range

Ferrous chloride dihydrate

40 - 60 oz/gal

Calcium chloride

20 - 35 oz/gal

Operating temperature

185 - 200°F

pH range

0.5 - 1.5

Current density (no agitation)

20 - 80 ASF

Current density (agitation)*

Up to 200 ASF

Anodes

High quality iron

Temperature

190 – 210°F

pH

0.2 - 1.8 using hydrochloric acid

 

*Air agitation must not be used. Air will oxidize the ferrous ions to ferric ions, which will cause rough deposits.

A few other comments:

1. Calcium chloride gives off heat when dissolved in water, so start with room temperature water.

2. After the bath is made up, add degreased steel wool to reduce ferric iron along with activated carbon to remove organic impurities. After this treatment, the solution is filtered into the plating tank.

3. Ductility of the iron deposit is improved at higher temperature, lowest pH and high current density.

4. Safety considerations are important because of the high operating temperaure and very low pH of the solution.

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