Q. I am making furniture and have settled on ½-inch galvanized metal rods for the legs, which I do not plan to paint. When I purchased these rods, they were coated with very thick grease. What is the best solution to remove the grease without affecting the zinc coating? I have access to denatured alcohol, lacquer thinner and any heavy-duty, all-purpose cleaners available at a hardware store. –C.H.
A. None of the solvents you mentioned will affect the galvanized coating, but the lacquer thinner may be the most effective at removing a majority of the grease. In chemistry, the saying is that “like dissolves like,” meaning the solvent that is chemically most similar to the grease will help to dissolve it. Many greases tend to be long-chain salts of fatty acids, meaning they may be derived from animal byproducts, and then the fatty acid end of the hydrocarbon is neutralized or saponified with a metal hydroxide like lithium or sodium. While the lacquer thinner would be effective at dissolving the long-chain hydrocarbon part of the grease, some aqueous detergent solutions may be also be effective in removing it, especially if you can make up a hot solution and immerse the parts in there for several minutes. A mild detergent will not attack the galvanized coating and may boost the overall cleaning effectiveness compared with the solvent alone.