A coating composition comprising zinc and a binder composition having an SiO content of from 5 to 40 percent on a weight basis which is obtained from the cohydrolysis and cocondensation of a mixture containing a silane selected from the group consisting of in which R and R' represent hydrocarbon radicals having up to 10 carbon atoms, R is a divalent hydrocarbon radical having from 2 to 6 carbon a