plating, anodizing, & finishing Q&As since 1989
Brass staining (probably due to cleaners and lubricants)
January 17, 2012
I have some brass components that are staining in grey patches on the surface after cleaning.
They are turned and then ground to a smooth finish in grinding fluid. They are then cleaned at 60° C in a supplier-recommended cleaner.
We have been using this process unadjusted for years but the brass has suddenly started staining. We have two different brass suppliers and the staining is occurring on both.
It is a complex proprietary brass alloy including +-58% Cu, 36% Zn, 2% Al, 1% Mn, 1%Si, <1% Fe, <1%Sn, 0.5% Pb. I will try to post the exact alloy composition later.
- Durban, South Africa
January 23, 2012
Hmmmm. Read this over a couple of times and my only conclusion is that something changed in your environment. Most likely your air flow may have contaminates from from either a new machine or a change in cutting fluids nearby or where the materials are stored before use.
retired business owner - Hatboro, Pennsylvania