Trivalent Chrome Electrolyte testing in lab

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A. You have to use the kind of anodes that the vendor suggests, Kelly, but maybe platinum clad titanium will work. Although still quite expensive, I think you can find those anodes used, and for a fraction of that $1000 each.

Ed. note: Sorry for the awkward use of the word "used"; I didn't actually mean to suggest buying anodes 'second-hand', but I can see from the responses how it was read :-(

A. Kelly, It appears that you bought that electrolyte second hand, not directly from its original manufacturer. Maybe you should contact them for an opinion. Guillermo Marrufo Monterrey, NL, Mexico A. I would urge caution in the purchase of used iridium clad anodes. A reputable company is probably not getting rid of them. A company that is going out of business fairly probably did not take the finest care of their equipment. Junkies are simply middle man in the purchase, and quite a few of them go by the motto that once you buy it, it is yours. I would be moderately surprised if you could not find your desired anodes from a reputable anode Mfg for less than 1 K per anode. Your required mesh size, plating thickness and shape will have a lot to do with the exact price. Remember, there is a difference between "clad" and "plated". James Watts - Navarre, Florida

A. Major proprietary plating chemical suppliers in US do supply trivalent chromium plating process which produce Cr deposit similar to Cr6+ process.

Trivalent systems can save an electroplating shop money in a number of ways:

1. Lower Metal Concentrations - Chromium concentrations in trivalent plating baths are typically less than 1 ounce per gallon (oz/gal). Hexavalent chromium concentrations are 15 to 40 ox/gal. Lower heavy metal concentrations mean less chrome dragout, and thus, lower waste treatment costs and less hazardous sludge generated in trivalent systems. Reducing sludge quantities also saves you money in haulage and disposal fees.

2. No Reduction Step - By installing a trivalent system, you avoid the need to reduce hexavalent chrome wastes to their trivalent state. Since three pounds of sodium metabisulfite are required to reduce each pound of chromic acid, significant quantities of chemicals, as well as equipment and labor costs, are eliminated by switching to a trivalent system.

3. More Parts Can Be Placed on a Rack - Trivalent chrome chemicals produce a high quality plate even when rack densities are increased 15% above those for hexavalent chrome systems.

4. Lower Current Density - Lighter weight, less expensive racks can be used to carry the lower currents. Simple hooks made out of hard drawn copper wire have also worked well in trivalent systems. Use of such hooks eliminates the expense of designing and special ordering custom parts racks.

5. Fewer Rejects - The throwing power of trivalent chrome is excellent. It is almost impossible to burn parts, too, according to satisfied shop owner, even with current densities above 100 amp/sq.ft. Trivalent systems do not experience the white washing problems that hexavalent systems do.

6. Reduced Dragout - Trivalent chrome baths are far less viscous than hexavalent chrome. Less solution clings to the parts that are withdrawn from the bath. This reduces both treatment expenses and materials costs for the makeup chemicals.

7. No Fumes - When you stand next to a trivalent chrome plating tank, you notice an immediate difference. There are none of those eye-stinging, throat-irritating fumes that are emitted from a chromic acid bath. The hexavalent chromium in those fumes is a suspected carcinogen. Besides being unpleasant to breathe, the fumes present a danger to personnel and to the environment surrounding the shop.

8. Reduced Liability - Use of hexavalent chromium constitutes a liability to the shop due to the dangerous nature of the chemical. Spills and other accidental releases of hazardous wastes can lead to lawsuits that might have been avoided if safer chemicals were used.

? Thanks David! I don't debate your list of advantages (although every process also has offsetting disadvantages. But can hard chrome (as opposed to decorative chrome) be done from trivalent baths of today's technology. My understanding is that the process is still only suitable for coatings of a few millionths of an inch thick, not several thousandths. Are you aware of a commercial installation doing hard chroming? If so, what thickness of chrome are they depositing? Thanks again!

A. Liquid Development Corp. is, to my knowledge, the first and probably the only company that claims to have a system to produce hard and thick (over half a thousandth) chrome deposits from a trivalent chrome solution. It is a brush plating system and the deposit is claimed to surpass conventional hex chrome in wear resistance three times. Guillermo Marrufo Monterrey, NL, Mexico Ed. note June 2016: Liquid Development Corp. was bought out by Sifco. Hi Ted, I agree with you that trivalent hard chrome plating is still in developing stage with the most problematic issue on Cr3+ oxidize to Cr6+ at anode and efficiency drop due to neutral salts build up. Some suppliers already employ regeneration system (prevent formation of Cr6+) and pulse plating to obtain a thousandth of an inch corrosion-resistant hard chromium deposit. Small scale installation (beta test) is done in some plating shops here (South-East Asia). David Shiu - Singapore

"Chromium Plating"
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Thanks Guillermo. Thanks David.

Scott may find Weiner & Walmsley interesting.
but it was published in 1980 -- at just about the beginning of practical trivalent chrome plating.

Regards,

? Hi Adam. Please introduce yourself, your overall goal, and where you got this formula so we can understand how best to try to help you. There is nothing wrong with you trying to do whatever you want to try to do, but we don't really know exactly what that is :-)

For example, do you already know that people generally simply buy their trivalent chromium plating solutions from specialist companies which have spent decades developing them, and the formulations are not public knowledge? Trivalent chrome often requires special apparatus like diaphragms to separate the anolyte from the catholyte, as well. Are you confident you've done proper preparation to the copper to make sure it is ready to accept chrome plating?

You may know 10 times as much about trivalent chrome plating as I'll ever know; maybe you are a chemist who has already industrialized trivalent chromium plating solutions, but we readers don't know quite where to start until you tell us :-)

Thanks & Regards,