Is it possible to remove the surface smear of lead from machined brass products?If so, what are the methods and the environmental concerns for disposal of the by-products? J.H.
I believe it is possible to use a strong, alkaline cleaner for the removal of some of the lead products. The cleaner should not be inhibited, otherwise that will interfere with the removal of some of the base materials. Additionally, in the high pH, uninhibited product will attack the brass parts and generally will appear to be moderately to heavily oxidized, depending on the amount of dissolved oxygen in your bath. An electrolytic cleaning tank may be an option to do the operation more quickly. Depending on what other processing you are doing with the parts, it may require an acid cleaning for removal of the oxide from the brass. I would suggest consulting the Products Finishing Directory or checking online at www.pfonline.com/suppliers.html, then searching under Cleaning Chemicals, Aqueous.
Dissolving the lead will likely present some difficulties with your waste treatment system, though. Once the material is in solution, it will have to be removed from that liquid prior to discharge. The level of removal depends on the regulations governing your facility, although for lead it will be very low. Two possible options would be to precipitate it and then filter the solid, or use an ultrafilter/reverse osmosis system to remove all impurities to a very low level. The selection of options depends on the volume of wastewater you have to treat. I would suggest contacting somebody knowledgeable with your regulations and treatment options prior to starting this operation.