Case Study Series

Spotting On Brass Parts.
–Jason Schwartz

Q: Can I recover parts that have spots on them?

A: Yes. For parts with white spotting, recovery is relatively easy. Rinsing the parts thoroughly with clean water will remove most white spotting. For spots that are a little tougher, running them through another cleaning process should take care of the issue. For parts with corrosion or dark spots, an acidic cleaner is usually needed. Using a citric acid product like KYZEN M6093 will generally remove dark spots that have not pitted or gone below the surface. For spots that are more than superficial, a traditional brass polishing process may be able to recover your parts. Getting more aggressive than citric acid on the chemical side yields mixed results. Sometimes, it helps recover parts, other times, it damages them further.

Q: Spotting seems to come from either the water quality or corrosion caused by humidity from the aqueous process. Will solvent cleaning work?

A: Absolutely. Solvent cleaning takes water and humidity out of the cleaning process and helps reduce or eliminate in-process corrosion. Also, because most of the white spotting comes from materials that are left behind in the water, solvent cleaning can help eliminate white spotting as well. It is best to work with your chemical supplier to determine which process is best for your parts and your plant.

Q: Are there corrosion protection options for solvent?

A: Yes! Solvent-based corrosion inhibitors tend to be wax or oil-based as opposed to watersoluble CP options found in aqueous products. As such, they leave a thin film on the parts that provide a physical barrier between the part and the moisture in the air. Although they work differently than aqueous-based CPs, they can be just as effective or even better.

Q: I have spots on my parts from dried on coolant, which won’t wash off. Is there anything I can do?

A: Yes. If parts have been left to sit around overnight or over a weekend, dried on coolant can prove especially difficult to remove. In chemistry, we have a saying that “like dissolves like.” One of the best ways to remove these spots is to soak the parts in fresh coolant before washing them. The fresh coolant will loosen up/ partially dissolve the spots, and your regular cleaning process should be able to take care of the rest.