A base-neutralized, water-diluted coating comprises (A) a polyhydroxyl-functional resin of an acrylate resin or an oil-free polyester containing urethane groups, (B) an amino resin partially etherified with an alcohol, (C) a basic neutralizing agent, (D) water, and (E) a water-insoluble crosslinking catalyst of a strong organic or inorganic acid such as p-toluenesulfonic acid blocked with a monoepoxide, diepoxide or lactone.