In one of our acquisitions, we bought out a brass giftware manufacturer and his unsold stock. The products consist of brass objects with smaller detail parts soldered on to them. The warehouse is full of these pieces that are in various stages of corrosion (tarnish). Some of the pieces are tarnished black. We are looking for ideas to remove the tarnish and not the details. After they are polished, they will be lacquered.
We have had various suggestions to remove the tarnish. One such suggestion was, “... grit-blast. If you then want to paint them, you are all set as the brass now has ‘tooth’ to hold the paint, and if you don’t want to paint and use a clear lacquer instead, you can polish it with beads in the grit blaster and clear coat it.” Another suggestion was, “use a commercial brass cleaner, but if there is a clear coat, you will need to strip it first, and you can get somewhat uneven tarnish removal.” A third suggestion was using an abrasive cleaner applied by brush. Also suggested was using an automotive polishing compound. All these latter suggestions were rejected as being too labor intensive. Can you suggest something? S. V.
As you already noted, hand tarnish removal is too labor intensive. Instead, you want to process large numbers of products in a short time. If there is any clear organic “protective lacquer” coating on the products, it must be removed. This can be done using solvents or paint stripping chemicals. The solvent or paint strippers used will depend on the type of coating to be removed. After all the organic coatings are removed, use a bright dip to remove the corrosion products. Suppliers of paint strippers are listed under Paint Strippers, chemical, on page 352 and 353, of the Products Finishing 2005 Directory & Technology Guide. Bright dip chemical suppliers are listed under Bright Dips, on pages 268 and 270, of the same directory.