Brush Plating of Decorative Chrome (portable/pen/tampon plating)

• Topic 56583 "Can hard chromium plating be spot repaired?"

A. Hi Jorge, probably not.

Weiner & Walmsley "Chromium Plating" only has a half-page about brush plating but says the solution is Cr(C₂O₄)₃(NH₄)₃ in methyl alcohol or hydroxylamine with an organic amine wetting agent.

Rubinstein [affil link to info/book on Amazon] includes data sheets for 3 different brush plating solutions but they are proprietary so only limited information on the composition is available. Good luck.

Luck & Regards,

A. Unfortunately, the answer to your question is "it depends" on your criteria. Brush plating is probably 10 times more sensitive to operator influence than tank plating. Operators are typically very poorly trained. (NOT ALWAYS)!

0.001 of say nickel, is a very columnar vs laminar for tank plating. Therefore, it is easier to have a vertical void that does not show.

Brush plating can be an excellent plating process, but normally is not the equal to a tank process on OEM. Conversely, try to take a shaft out of a large boat, That is why the US Navy has brush units on many of its ships.

A. All things being equal, the brush plated chrome will be as durable as tank plated chrome. The caveat is, of course, that things are not always equal. Typically, a brush plated deposit is not as thick or as uniform, and the surface preparation prior to plating is not as good.

With respect to toxicity, etc., brush plating solutions tend to be MORE concentrated than their tank brethren.

A. One of the beauties of brush plating is that for most applications it does not need grinding after plating. Cobalt is certainly whiter than nickel. Adding tungsten makes it harder. For a non chrome, that is the best you will get. Is it possible that you are burning the plate in grinding? Nickel is relative too soft for grinding and it is not recommended in many applications. If you must post grind, I would try a wheel with a more open structure and a binder that breaks down faster. At least one brush plating company sells a trivalent chrome that you could apply after grinding for a chrome finish. It is slightly off color, faint blue, and can only be applied in very thin coats.

A. It is a good rule of thumb to start with whatever chemicals/process that your equipment MFG sells for their equipment. After you have got the process down pat, then start looking for alternative sources. PS, brush chrome is a very very thin cap layer.

A. For tank plating, as you surely know, there is hexavalent and trivalent chrome. For brush plating, only trivalent has been thoroughly developed. It can be plated to some 0.001" or perhaps even more, though its color resembles more the nickel. To my knowledge what Jim said is correct hexchrome can only be applied in very thin caps before the brush, wrapping and anode reactions start decomposing and plating stops. Final result is always disappointing, specially if you want to match existing chrome to its blueish cast.