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Abstract

Low alloy steel tubes are decarburized, heavily diffusion chromized and heavily diffusion aluminized to protect them against sulfidation. For the diffusion they can be supported upright with one end on layer of diffusion-coating pack on floor of a retort. Surface portions that are to be welded are covered with masking layer that prevents diffusion coating, or with inert layer that reduces the amount of coating. Diffusion aluminizing can also be applied to foils and powder to make pyrophoric product after leaching out much of the introduced aluminum. Powder can also be diffusion boronized. Pyrophoric boron-containing iron or nickel powder mixed with Ba(NO.sub.3).sub.2 will ignite to cause generation of large quantity of NO.sub.2 gas, and generation is improved when powdered boron and/or oxidizer like NaClO.sub.3 is added. Pyrophoric articles containing substantial alloyed boron can be placed in good thermal contact with cool heat sink and exposed to air to stabilize them so that they do not begin to pyrophorically react unless heated to over 70.degree. C. Magnesium powder mixed with powdered boron and Ba(NO.sub.3).sub.2 makes explosive composition.

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First Claim