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Solutions to Problems in blackening finished parts

We procure metal parts from subcontractors after blackening in which we find some white patch formation and also the color differences in lot to lot basis. As the subcontractor couldn't find out the reason for this problem we wish to analyze the reason for the same.

Hence we request info on blackening process which should have a gloss finish without using oil.

Please suggest how to start analyzing the reason for the problem.

Ravi janardanan
- Chennai, TamilNadu, India
2000

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Ravi

The white powder is an probably the caustic leaching out, now some time just better rinsing is the problem you can also purchase a rinse aide / sealer for the final rinse, sometimes there is almost no way to stop the leaching as to the way parts are made,

The different shades can be caused due to concentration or penetrant, temperature, time, different grades of steel (different hardness, materials different shades).

Chris Snyder
plater - Charlotte, North Carolina
2000

Chris is absolutely right. However, there are ways to cover up some of these problems so that quality and color are more consistent. One way is to post dip parts in a dry oil. Another is to use a black wax or black polymer coating.

Gene Packman
process supplier - Great Neck, New York
2000

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