Q: I am looking for a pre-treatment/cleaning process (preferably spray, as opposed to a dip method) for beryllium copper parts. What cleaning process would you recommend for this material? In addition, would a bright dip be ideal for a last bath within the process? J.S.
A. I do not have any direct experience in finishing beryllium copper, but from the little bit of information I found on the material I would expect it to behave similarly to copper from the standpoint of finishing. The alloys have beryllium added at 0.5–2.9% by weight to impart improved strength and, at lower concentrations, improved electrical conductivity. If we assume your parts will behave like copper parts in finishing operations, it’s a matter of what contaminants are on your surface and the level of cleaning that you need to achieve.
An aggressive but effective bright dip to clean most copper alloys is a combined nitric and sulfuric acid operated at room temperature. Concentrations could be about 20% by volume of each acid. If you need a less aggressive cleaning, a citric acid solution would provide a clean surface with much less in the way of hazardous chemical exposure to your employees and a less hazardous solution to dispose of when it comes time to dump the bath.
Somewhere upstream in this line should be a cleaning step to ensure removal of any grease and oil before a bright dip; otherwise, the acids will not etch the surfaces uniformly. The residual bright dip should not be left on the surface in any circumstance (regardless if it is the nitric/sulfuric combination or the milder citric acid cleaner) since that will lead to additional etching and eventual staining as it dries on the surface.
The final steps should be a clean water rinse and, depending on your water quality, possibly a deionized or reverse osmosis water rinse to insure the water does not lead to spotting after drying.