Low-cure powder coating compositions are disclosed. The compositions comprise a polyepoxide and a material having the structure ##STR00001## wherein R.sub.1 is an organic radical having 6 to 25 carbon atoms; R.sub.2 is an organic radical having 1 to 20 carbon atoms; R.sub.3 and R.sub.4 are independently alkyl or phenyl groups having 1 to 8 carbon atoms; Z is oxygen or nitrogen, and when Z is oxygen R.sub.5 is absent and when Z is nitrogen R.sub.5 is hydrogen or is ##STR00002## and n is 1 to 4. The material can optionally be reacted with an acidic hydrogen-containing compound. The compositions are curable without the use of crosslinking agents or accelerators. Methods for coating a substrate using these compositions, and substrates coated thereby, are also disclosed, as are additional catalysts useful for the same purpose.