| Search our quarter-million Q&As |
Home of the finishing HOTLINE since 1989
-----Need expert advise on reducing/ eliminating zinc plating defects
We have small parts made from Cold Rolled Carbon Steel (Mild Steel) and then Zn Plated for 10-12 µ and then trivalent passivated.
Some of the quantity starts having black spot and white rust on surface within 3-4 month. These parts are barrel Zn plated.
Similarly we have screws of M3x12 or M4x15 like small size and they are heat treated for 8.8 grade quality and then Zn plated like above. They also start white rust formation on threads.
Please give me your expert advise on reducing / eliminating the problem.
group general manager looking after plating shop - India
October 5, 2009
October 7, 2009
Hi
First, do accelerated salt spray test on your parts to obtain whether your corrosion requirements are fulfilled with your existing process setup and bath parameters or not.
Secondly, being the Cr3+ passivations are not having self-healing properties like Cr6+ passivations, ask your chemical supplier to provide inorganic sealant after Cr3+ passivation for your parts.Which will give longer life against corrosion.
Note: Please try to avoid zinc plating for fasteners where Hydrogen embrittlement issues are very likely to happen for those parts.
Recommendation: Provide Geomet or Magni coating for fasteners.
Regards
Vijendran
- Chennai, Tamil Nadu, India
adv.
Sorry! Finishing.com is temporarily Read-Only.
Ted Mooney is retiring but I have several offers to take it over.
We're working hard to make sure we find it the best new home.