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copper sulphate test failures on hot rolled steel

October 25, 2011

Q. We produce automotive parts manufactured from HOT ROLLED STEEL
Our cleaning process involves alkaline washing and amine rinse following the stamping operations and prior to additional steps
To verify the cleanliness of the steel surface we take parts from the end of the wash line and immerse in copper sulphate [on eBay or Amazon]testing solution (Made in the standard fashion)for 20 to 40 seconds at room temperature
A result showing complete copper coating is our indication that there is no oil residue on the parts.
From time to time we have parts failing this test when there appears to be NO OIL on the surface.
now 95 % of parts pass this test.
Our question is

WHAT ELSE COULD BE INHIBITING THE COPPER "PLATE" ON THESE PARTS
ALUMINUM (Perhaps AK Aluminum killed stock)OR

Amine does NOT inhibit the coating and we are looking for root cause which all points to issues that may be present on the steel prior to stamping

Perhaps you can identify what MORE NOBLE (Than iron) substance you might look for in these circumstances

We would appreciate any thought process might be in identifying a "Root Cause"

Peter White
research - Detroit Michigan USA

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Q. We run copper sulphate testing on parts to ensure cleanliness
The results have been inconsistent and show no copper deposition when there is no oil present
Can you advise what other contaminants might be responsible to cause this lack of coating
Peter

PETER HUSTED
Operations Manager - Charlotte, North Carolina, USA
July 18, 2013