C - Chemistry – Metallurgy – 23 – C
Patent
C - Chemistry, Metallurgy
23
C
117/71
C23C 10/50 (2006.01) C23C 10/02 (2006.01) C23C 10/04 (2006.01) C23C 10/30 (2006.01) C23C 10/38 (2006.01) C23C 10/40 (2006.01)
Patent
CA 1144431
IMPROVEMENTS IN METAL COATING Abstract of the Disclosure Ferrous metal or titanium is coated with a mixture of phosphoric acid, chromic acid and magnesium salts of these acids, and separately with aluminum flake applied as upper or lower layer with or without hexavalent chromium compound like magnesium chromate, and/or metallic magnesium, both layers being baked, to provide excellent resistance to attack. The aluminum flake layer can also be used without the other layer. Diffusion aluminizing of the ferrous metal before the coatings produces even better results. Very good masking of pack diffusion aluminizing or chromizing, on any metal, to keep portions from being metallized is effected by multi-layer localized coating the lowest layer being depletion-reducing masking powder mixed with non-contaminating film-former such as acrylic resin, and upper layer or layers being of non- contaminating particles like nickel or Cr2O3 that upon aluminizing become coherently held together to form a secure masking sheath. Aluminizing pack can then be re- used. Film-former can be dissolved in volatile solvent, preferably methyl chloroform, in which masking powder or sheath-forming powder is suspended. Chromizing can be performed before aluminizing for greater effects, and pack chromizing in gas-tight retort under inert gas such as argon, using low activity throw-away pack of highly diluted mixture of chromium, nickel and aluminum gives chromized coating exceptionally free of undesired oxides and of alphachrome. Differential chromizing can also be practiced to produce thinner chromized case in desired locations. Low alloy steel conduit can be internally chromized and/or externally chromized or aluminized to make it more desirable for use as high pressure steam boiler heat exchange tubing. Nickel articles aluminized with deep Ni2Al3 layer that has outer skin more heavily aluminized can have aluminum correspondingly leached out from outer skin only.
280111
Alloy Surfaces Company Inc.
Macrae & Co.
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