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Blotchy black oxide

WE HAVE SMALL STAINLESS STEEL CASTINGS THAT WE SEND OUT FOR BLACK OXIDE COATING PER MIL-DTL-13924 [on DLA] CLASS 2 OR 3.

NORMALLY, THE PLATER HAS NO PROBLEMS WITH THESE PARTS BUT THIS TIME HE HAS BEEN UNABLE TO GET FULL/UNIFORM COVERAGE ON THIS BATCH.

OTHER STAINLESS PARTS RUNNING THROUGH THE SAME LINE AT THE SAME TIME HAVE GOOD COVERAGE.

THE FOUNDRY STATES THAT THE PARTS CONFORM TO THE PRINT AND THERE IS NO RESIDUE.

WHAT ASPECTS OF THE BLACK OXIDE PROCESS SHOULD WE BE CONSIDERING IN ORDER TO SOLVE THIS PROBLEM? HAS ANY ONE EXPERIENCED SIMILAR RESULTS AND FOUND A SOLUTION? THANKS,

ROBERT NICHOLS
VALCOM - GUELPH, ONTARIO, CANADA
2004

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