IRON IN CHROME TANK

Q. I chrome plate cast iron and use steel anodes. So of course I have a problem with iron in my bath. How would you suggest that I remove the iron? Any help would be appreciated! J.P.

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A. There are a number of ways to remove iron from a chromium plating bath.

Perhaps the most common method is to use a porous pot. The “fancy” name for this is ion transfer technology. In a survey conducted by the National Metal Finishing Resource Center (NMFRC; www.nmfrc.org), 10% of the chromium platers who responded used this technology to remove iron from their plating baths. I am aware of only one source of porous pot systems in the U.S. You can find the company online by plugging “Porous Pot” into your favorite Internet search engine.

Another approach is to use ion exchange equipment for iron removal. The above mentioned survey indicated that about 3% of the respondents used this process. There are a number of vendors of this equipment. A search of PFOnline will give you the names and contact information for a number of companies.

A third process, membrane electrolysis, sometimes called electrodialysis, is used by a few chrome plating companies. It is similar to the porous pot technology except that ion-specific membranes are used instead of porous pots. An Internet search using the term “membrane electrolysis chromium plating” will give you a number of vendors who can supply the equipment needed.

Of the three technologies mentioned, the porous pot technology is the least expensive.

Now I have a question for you: Why are you using steel anodes?

If you are serious about chrome plating, you must use an anode that will not add iron to your plating solution. Lead alloyed with?small amounts of antimony or tin is typically used. You should do the same.

You can find additional information on chromium plating in the Products Finishing 2008 Directory & Technology Guide, under the articles tab at www.pfonline.com.