Iron Plating Questions and Answers

Iron Plating Baths

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? 

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.

Formulations

Q. Can you offer a formulation for an iron plating bath? 

A. There are different formulations for an iron plating bath in the plating literature. Here's one that works well.

Component	Concentration
Ferrous fluoborate	32 oz./gallon
Ammonium chloride	2 oz./gallon
Boric acid	4 oz./gallon
Operating Controls	Range
pH	3-3.4
Temperature	150-160°F
Current density	2-90 asf