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topic 1224

Alkaline Cleaning


Q. Our finished plated hardware is put through a pre-clean prior to use. This pre-clean is a mild alkaline cleaner followed by a low pH surfactant. While the part is in the surfactant you can see the part start to tarnish. This will happen on EDNi, Chrome, or Silver. Has anyone had a problem with coatings tarnishing during pre-clean, and does anyone have a suggestion on how to eliminate the problem.

Garry Pickett
aerospace - Los Angeles, California


? Gary:
Just what metal are these parts that are "pre-cleaned"? Is this done pre-plate? What is the purpose of the acidic solution? Is it to dry the parts, rinse them spot free, seal or rust prevent? Those answers may help me to help you.

Craig Burkart

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Craig Burkart
- Naperville, Illinois


A. Gary, The process you are describing tends to let me think this is a preplate operation, however I think this is after plating. If so, why are you using the low pH surfactant? If this operation is to clean residual manufacturing soils I would suggest staying with the mild alkaline solution but go directly to a R/O or D.I. rinse. The make up of the water will have less of an acidic state than what you have now. Bob

bob utech
Bob Utech
Benson, Minnesota

A Guide to High Performance Powder Coating
by Bob Utech
[link is to Amazon]


Q. Need recommendations for cleaning process/chemical (alkaline) for removing ash and heavy rust/scale after parts are cleaned thermally.

Steven e Morgan
engine systems/ - Latham, New York

A. Hi Steven. Assuming that you are talking about steel parts, you'll probably want an alkaline electrocleaner operating at about 200 °F. The parts will probably be anodic.

Something that you may know, but other readers may not, is that people don't formulate their own alkaline cleaners today. Rather, they buy a proprietary from a plating process supplier for two reasons: firstly, so they get the benefit of the suppliers decades of development experience because cleaners are fairly complex, involving saponification, wetting and emulsification, deflocculation, chelation/sequestration, buffering, and inhibition. Second because the supplier will have a test lab to run samples; you don't want to design a cleaning line based only on theory, and want to build a line which employs chemistry that you have tested.

After the alkaline cleaning and rinsing, you will require an acid activation step. Often 25% (or so) HCl will serve, but again testing is required. Good luck.


Ted Mooney,
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Ted Mooney, P.E.
Pine Beach, New Jersey

Cleaning oily parts for brush plating

September 16, 2016 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I have a main shaft from an old motorcycle that is worn a bit. I'd like to brush plate the worn spot with nickel to build it up a few thou. Being as how this has been in oil its entire life it might be tough to get it degreased. Someone on here mentioned a hot alkaline bath; what is meant by alkaline bath? I also read I might have to hit it with sulfuric acid. After that would I need to copper plate first, then nickel? Thanks in advance

dave smith
- phoenix Arizona usa

September 2016

A. Hi Dave. I'd scrub it with a tampico brush and pumice and a solution of hot water and dishwasher detergent. Then I'd dip it in 25% or so HCl. Then nickel plate it.

Hopefully, before thinking you can successfully plate a few thousandths of an inch of nickel on a shaft, you've acquired a good bit of experience on scrap parts. Because it's one thing to brush plate a little gold onto an emblem that a plating shop has done a fabulous job of pre-plating with nickel for you, and quite another to nickel plate a dirty, raw steel main shaft. Alternately you can have a plating shop do it for you. Good luck.


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Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

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