Abstract: Low alloy steel tubing is decarburized, chromized and then aluminized with or without masking at the sites at which the tubing is to be welded in place, to greatly increase resistance of the tubing to high temperature oxidation and sulfidation. Low surface aluminum content after aluminizing makes it easier to weld at that surface.

Abstract: Very good masking of pack diffusion aluminizing on any metal to keep portions from being diffusion coated, is effected by localized coating the lowest layer of which is depletion-reducing masking powder that can have same composition as substrates, mixed with non-contaminating film-former such as acrylic resin. The upper coating layer can be of non-contaminating particles like nickel of Cr.sub.2 O.sub.3 that upon aluminizing or chromizing become coherently held together to form a secure sheath. Such sheath can also be used for holding localized diffusion-coating layer in place. 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. Aluminized cases are stripped from superalloys by alternating dips in fluoride-containing and fluoride-free aqueous nitric acid.

Abstract: Pyrophorically activated metals are suitable catalysts for electrolyzing water and for other reactions in which nickel or platinum are catalysts. Pyrophoricity can be eliminated without destroying the catalytic effects. Protective coverings can protect and preserve the pyrophoricity. Raney type activation leaves a little aluminum in the activated metal and this aids in catalytic action.

Abstract: Pyrophorically activated surfaces of metal foil or screen, prepared by diffusing into surface a selectably removable second metal that is then selectively removed as by leaching, can be covered with reactive or inert materials. Reactive materials such as easily ignited metals or carbon or decomposable chemicals increase the heat generated by pyrophoric action. Inert materials slow down or prevent pyrophoric action. Pressure-sensitive adhesive tape in which the adhesive is of the non-transfer or transfer types can be adhered to pyrophorically activated surfaces to slow down action or to adhere material that reduces or increases severity of pyrophoric action. Pyrophoric Ni can be preserved for many months in alkaline solutions such as aqueous KOH, NaOH and triethanolamine. Pyrophoric Fe is prepared and preserved in aqueous alkaline stannite. Even better preservation is obtained for Ni and Fe with glycerine, ethylene glycol, triethanolamine and propylene oxide.

Abstract: Ferrous metal or titanium or aluminum is coated with a mixture of phosphoric acid, chromic acid and magnesium salts of these acids, as well as with aluminum flakes, or coated with a mixture of aluminum flakes and magnesium chromate or dichromate, to provide after baking excellent resistance to attack. Aluminum-silicon alloys containing about 10 to about 15 weight percent silicon give better results than ordinary aluminum, particularly when the aluminum is in powder form; and when coated products are given a burnishing treatment. Very good masking for pack diffusion aluminizing or chromizing on any metal to keep portions from being diffusion coated is effected by localized coating, the lowest layer of which is depletion-reducing. The upper coating layer can be of non-contaminating particles like nickel or Cr.sub.2 O.sub.3 that upon aluminizing or chromizing become coherently held together to form a secure sheath. Such sheath can also be used for holding localized diffusion-coating layer in place.

Abstract: A metal web having a pyrophoric surface is coated by a solid or liquid that does not block the pyrophoric property and undergoes a pyrophoricity-intensifying exothermic change when subjected to the pyrophoricity of that surface.

Abstract: Diffusion coating of internal surface of workpiece accessible only through very narrow passageway, is simply effected by coating that surface with uniform layer of particles of the metal to be diffused into it, and then holding the thus-prepared workpiece at diffusion-coating temperature in a diffusion-coating atmosphere.

Abstract: Chromized nickel- and cobalt-based superalloys have alphachrome phase formed during chromizing, and the amount of that phase is diminished by one or more treatments with alkali-permanganate solution and intervening removal of permanganate reaction product film as by acid dip. A kit of such solutions can be prepared. Low-alloy steel steam boiler tubing can have chromized interior and aluminized exterior, and long lengths chromized without a perfectly sealed retort around it can have end caps fitted with extra pack to reduce oxygen penetration to interior. Chain saw cutter blades can be chromized and carburized. Stripping of aluminized coatings from superalloys with fluoride-containing nitric acid solution is improved by follow-up treatment with fluoride-free nitric acid solution.

Abstract: Diffusion chromizing of nickel-base superalloys is effected with essentially no formation of oxide or alphachrome, even in a high-volume diffusion coating pack, by use of a pack consisting essentially of, by weight,about 2 to about 3% aluminumabout 3 to about 6 times as much chromium as aluminuma mixture of cobalt and nickel in a combined amount about 10 to about 20 times the amount of aluminum, the amount of cobalt being from about 1/3 to about 4/3 the amount of nickelthe balance of the pack being essentially inert filler and activating material. The use of a magnesium halide activator with such pack extends the improvement to the application of heavier chromizing cases. Pack can be of fluent type, particularly where workpiece is partially masked, and masking can be colored to provide visual contrast. Metals not requiring chromizing can be aluminized and top coated with slurry of flake aluminum in aqueous solution of CrO.sub.4.sup..dbd., PO.sub.4.sup..tbd. and Mg.sup.++.

Abstract: Diffusion coating a substrate metal with a different metal, such as aluminum and zinc, that is then chemically removed from the coated substrate, provides the residual metal with a very desirable catalytic surface. At least about a third of the removable metal can be dissolved out. Platinum wire screens activated in this way make effective exhaust catalysts for automotive engines. Chromium-rich coating for protective purposes can be applied on a superalloy, diffusion coating in a pack that in addition to the chromium to be diffused, also contains at least about 3% Ni.sub.3 Al. Also the formation of alpha-chromium is reduced when the pack diffusion is carried out in a retort effectively not over five inches in height. Pack aluminizing in the presence of chromium makes a very effective aluminum- and chromium-containing top coating over platinum plated or platinum coated nickel-base superalloys.

Abstract: Chromized nickel- and cobalt-based superalloys have alphachrome phase formed during chromizing, and the amount of that phase is diminished by one or more treatments with alkali-permanganate solution and intervening removal of permanganate reaction product film as by acid dip. A kit of such solutions can be prepared. Low-alloy steel steam boiler tubing can have chromized interior and aluminized exterior, and long lengths chromized without a perfectly sealed retort around it can have end caps fitted with extra pack to reduce oxygen penetration to interior. Chain saw cutter blades can be chromized and carburized. Stripping of aluminized coatings from super-alloys with fluoride-containing nitric acid solution is improved by follow-up treatment with fluoride-free nitric acid solution.

Abstract: Roughening effect of low-temperature diffusion aluminizing of age-hardenable stainless steels, is offset by applying a nickel or cobalt plating not over 0.1 mil thick before the aluminizing.

Abstract: Roughening effect of low-temperature diffusion aluminizing of age-hardenable stainless steels, is offset by applying a nickel or cobalt plating not over 0.1 mil thick before the aluminizing.

Abstract: Diffusion coatings can be masked from portions of a workpiece by combination of layers, the outer one of which forms coherent strong shell that holds inner layer or layers in place. All ingredients of these layers can be materials such as nickel, nickel aluminide, chromium, chromic oxide (Cr.sub.2 O.sub.3) and inert diluent that do not contaminate superalloys or even low alloy or plain carbon steels. Such a holding shell can also be used to retain on a workpiece surface a layer that causes formation of a diffusion coating. 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 Ni.sub.2 Al.sub.3 layer that has outer skin more heavily aluminized can have aluminum correspondingly leached out from outer skin only.

Abstract: Foil, wire and similar coherent bodies of catalytic metal are provided with catalytically active surfaces by diffusing a chemically removable metal such as aluminum or zinc into those surfaces and then selectively dissolving out at least about a third of the removable metal. Platinum wire screens activated in this way make effective exhaust catalysts for automotive engines.

Abstract: Aluminum diffusion can be effected from continuous coatings of leafing-type aluminum particles and such leafing coatings in very thin layers are more effective than coatings of non-leafing aluminum, with or without diffusion. Other protective metals in flake or leaf form can be substituted for or added to the leafing aluminum. Adhesion of the flakes to the substrate is greatly improved and can be effected at lower temperatures if the flakes are applied from a dispersion containing a volatilizable halogen-type carrier or an ammonium chromate. The leafing coatings can be sprayed on from aqueous dispersion containing wetting agents and if desired a polyethylenetrtrafluoroethylene and/or mixtures of phosphoric acid, chromic acid and magnesium, aluminum, calcium or zinc salts of these acids.

Abstract: In the pack diffusion coating of chromium into the surface of a superalloy, the formation of undesirable oxide inclusion is reduced when the diffusion coating pack contains at least about 3% Ni.sub.3 Al. Also the formation of alpha-chromium is reduced when the pack diffusion is carried out in a retort effectively not over five inches in height. Pack aluminizing in the presence of chromium makes a very effective aluminum- and chromium-containing top coating over platinum plated or platinum coated nickel-base superalloys. Aluminized nickel can also have its aluminum attacked and at least partially removed with aqueous caustic to leave a very highly active catalytic surface. Pack diffusion can also be arranged to simultaneously provide different coatings in different locations by using different pack compositions in those locations. An aluminizing pack containing a large amount of chromium provides a thinner aluminized case than an aluminizing pack containing less chromium, or less chromium and some silicon.

Abstract: Low temperature aluminum diffusion is more uniform when effected with a pack energized by aluminum chloride or other material that does not generate nitrogen, and gives food protection against marine corrosion of steels, and 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 and dispersed polytetrafluoroethylene particles. Such coating mixture is best applied over porous pre-coating of colloidal inert particles. Aluminized superalloy can be heated in air to whiten it, then cleaned to give product having more ductile case. Such coated superalloy can also be stripped of coating by aqueous HNO.sub.3 --HF--CrO.sub.3 bath.

Abstract: In the diffusion coating of aluminum onto brazed metal, the penetration of the aluminum into the brazing is reduced by conducting the diffusion coating with hydrated aluminum chloride, bromide or iodide as energizer, with the energizer preferably kept out of contact with the work being coated until the energizer volatilizes. This is particularly suited for aluminizing chromium-containing surfaces. Chromium diffusion coatings are less apt to form undesirable oxide inclusions when the diffusion coating is from a pack containing at least about 3% Ni.sub.3 Al. Also the formation of undesirable alpha-chromium is reduced when the pack diffusion is carried out with a retort effectively not over 5 inches in height. Pack aluminizing where the aluminizing is inhibited by the presence of chromium in the pack makes a very effective top coating over platinum plated or platinum coated nickel-base superalloys.

Abstract: Foil, wire and similar coherent bodies of catalytic metal are provided with catalytically active surfaces by diffusing a chemically removable metal such as aluminum or zinc into those surfaces and then selectively dissolving out at least about a third of the removable metal. Platinum wire screens activated in this way make effective exhaust catalysts for automotive engines.