Q. I plate high-polish brass parts that have been polished using a buffing compound that reaches high temperatures, resulting in the compound being caked-on. We hand-wipe clean using Stoddard solvent then electroclean, but this cleaning operation becomes very time-consuming as the quantity increases, and it is difficult to meet the customer’s needs. What is the best way to remove the buffing compound? D.H.
A. It sounds like your current cleaning method works well, but you are not able to keep up with the demand as the number of parts increases. To introduce more automation into your process, there are two aspects of the current process you will need to replicate. Buffing compounds contain very fine abrasives, often aluminum oxide or silicon carbide, that are suspended in a slurry compound, usually containing some organic components. Your current process is successful since it uses the Stoddard solvent as a cleaning agent to break down and remove the organic component, while your manual wiping method is effective at physical removal of the abrasive component of the mixture.
You should address both of those aspects in your new cleaning process. The mechanical component to your current cleaning process will be best replicated by replacing it with another mechanical process such as ultrasonics or agitation of the cleaning tank. Ultrasonics may require a higher initial investment, but could produce quicker and more effective results. The agitated tank would enable you to quickly move the parts through the wash solution or move the wash solution over the parts.
In the case of ultrasonics, you may want to consider changing the cleaning solution to a fully formulated aqueous cleaner. There will be surfactants that can break down the organic additives of the buffing component and solubilize water-based additives, and contain ingredients to suspend some of the fine-particulate abrasive so it will not redeposit back onto the part. Ultrasonics would provide the mechanical means you are looking for, and aqueous cleaners tend to be more effective in ultrasonics than organic solvent. This process would be most effective in a heated wash tank that will shorten the time for the cleaner to break down the buffing compound. Finally, an effective rinsing step would be necessary to remove the cleaner and any particulate still adhering to the surface. That could also be a heated, ultrasonic tank, or simply an ambient-temperature, still tank if the parts are coming out fully clean from the first stage.
A simpler agitated immersion tank (or spray-under immersion) may still use the Stoddard solvent as long as you are effectively handling the health and safety aspects of the system such as proper ventilation and handling of a combustible solvent.