Abstract: Low temperature aluminum diffusion is of better quality when effected with a pack energized by aluminum chloride or other material that does not generate nitrogen and is shielded from contacting the work pieces until after the pack is heated to energizing temperatures. The resulting aluminizing very effectively protects steels against corrosion in marine atmospheres, particularly when there is a chromate-type coating applied over the aluminizing. Highly effective chromate-type coating mixture consists essentially of aqueous solution of chromic and phosphoric acid also containing magnesium salts of said acids with or without dispersed polytetrafluoroethylene particles. The salts of divalent metals such as calcium, zinc, strontium, manganese, cobalt and nickel whose chromates are soluble in acid, can be used instead of or in addition to the magnesium. Such coating mixture is best applied over porous pre-coating of colloidal inert particles.

Abstract: Dispersion-strengthened nickel and nichrome protected by an aluminum diffusion coating over a chromium diffusion coating, have their resistance to oxidation at extremely high temperatures increased by including cobalt with the chromium diffusion coating. Aluminum diffusion can be effected with an energizer kept out of contact with workpieces by being confined in porous containers.