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Engineers(?) tampering with corrosion test results 1

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kenvlach

Materials
Apr 12, 2000
2,514
Came across a description of engineers tampering with corrosion test results
It deals with zinc plating that was salt spray tested per ASTM B117. To those unfamilar, at the end of the salt spray
"The specimens shall be carefully removed.
Specimens may be gently washed or dipped in clean running water not warmer than 38oC (100oF) to remove salt deposits from their surface, and then immediately dried. Drying shall be accomplished with a stream of clean, compressed air."

The engineers(?) were wiping off the white residue (zinc corrosion is white), asserting that it was salt. Pretty unprofessional. Was my response appropriate?
 
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Zinc plating on steel is often chromated for corrosion protection. Several grades of chromating offer different degrees of corrosion protection of the zinc.

The number of hours before white rust in the salt spray test is a measure of the quality of the chromate coating.
E.g., in thread338-164597, the minimum for Type II chromated zinc per ASTM B633 is 96 hours. White rust before this time constitutes failure. Many platers are having problems since switching from proven hexavalent chromium formulae to new, trivalent chromium (less hazardous to health & environment).

The number of hours before red rust (rusted steel substrate) is a measure of the quality of (zinc plating + chromate).
 
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