Vapor-deposited silica coatings could extend the life of the 20% Cr/25% Ni niobium stabilized (20/25/Nb) stainless steel fuel cladding of the U.K. advanced gas-cooled reactors. A chemical vapor deposition coating process developed originally to be undertaken at atmospheric pressure has now been adapted for operation at reduced pressure. Trials on this process have been pursued to the production scale using commercial equipment. The effectiveness of the silica coatings produced in providing protection to 20/25/Nb steel surfaces against oxidation and carbonaceous deposition has been evaluated.