Saponification is a chemical reaction that occurs when oil product is mixed with an alkali. The byproduct is soap ( The root word “sapo” in Latin is soap).
Alkyd-type coatings that are applied to galvanized metal (zinc) fail because the corrosion products of zinc are alkaline. Alkyd-modified coatings are very sensitive to alkalinity and a saponification reaction occurs at the zinc-alkyd interface. Check with your Product Data Sheet (PDS) for compatibility to galvanizing.