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Tarnish of electroless nickel over brass or alum. when ultrasonic aqueous cleaning
May 7, 2009We have thousands of parts Electroless Nickel plated and often they look fine before cleaning in a multi-stage ultrasonic cleaner. However, after processing in the ultrasonic cleaner (two stages of ultrasonics, one rinse, one dry -cleaner is Blue Wave Detergent # 25-I, 4 parts purified (Seattle city water through filters) deionized water to 1 part liquid detergent)). Many of the parts come out with brownish to blackish spots of irregular shapes. They kind of look like the variation you would get with water spots. Strangely, if we don't turn on the ultrasonics, we don't have this staining issue (though we have to soak them longer to get fingerprints etc. off of them). We are trying to get them clean for oxygen service. The brownish/blackish spots can be buffed off but that is labor intense and thins the surface.
Customer - Kirkland, Washington
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