Summary for gun blue discoloration Discussion
Gun blue discoloration on cadmium plated aluminum is the core issue in this thread. Sean Cahill says his company repairs scratches in cadmium plating on aluminum fiber optic connectors with Perma Blue Liquid Gun Blue, but recently the touched-up area has become noticeably darker than the surrounding cadmium and is failing QC. He asks what might be causing the change. The only reply shown is from Bill Grayson, who questions the practice itself and says he has a hard time understanding how gun bluing would be an allowable repair for a scratch. No technical cause is given in the excerpt, but the discussion suggests the repair method itself may be the problem and that the QC requirement is strict enough to reject the darker touch-up area.
My company makes fiber optic connectors for the military. Recently we are experiencing a problem with our aluminum parts coated with cadmium. If we get a scratch in the cadmium finish it will not pass through a QC inspection so we treat it with a little bit of Perma Blue Liquid Gun Blue
⇦ on
eBay or
Amazon [affil link] . In the past it has not been a problem as the discoloration from the scratch is hidden by the Gun Blue. Recently however the area of the Cadmium plating where the Gun Blue is applied is is becoming significantly darker than the rest of the cadmium finish and it also does not pass thru a QC inspection. Any ideas what could be causing this discoloration of the cadmium finish where the Gun Blue is applied to in recent weeks. Thanks for your help.
Sean Cahill
Fiber Optic Cable Assembly Manufacturer – Naugatuck, Connecticut, USA
2006
? I’m having a hard time understanding how BC gun blueing is an allowable repair for a scratch! ?
Bill Grayson
metal finishing – San Jose, California, USA