Abstract: This invention relates to an aluminum-zinc alloy coated ferrous base product which exhibits improved atmospheric corrosion resistance, and to the process whereby such improved corrosion resistance may be realized. The process is characterized by the steps of heating such coated product to a temperature within the single phase region for the composition corresponding to the aluminum and zinc of said coating, defined as .alpha. in the FIGURE in the accompanying drawing, preferably at a temperature between about 650.degree. F. (343.degree. C.) to 750.degree. F. (399.degree. C.), for a period of time to solution treat the aluminum-zinc alloy coating overlay, and cooling slowly to at least 350.degree. F. (177.degree. C.).

Abstract: This invention relates to an aluminum-zinc alloy coated ferrous base product which exhibits improved atmospheric corrosion resistance, and to the process whereby such improved corrosion resistance may be realized. The process is characterized by the steps of heating such coated product to a temperature within the single phase region for the composition corresponding to the aluminum and zinc of said coating, defined as .alpha. in the FIGURE in the accompanying drawing, preferably at a temperature between about 650.degree. F. (343.degree. C.) to 750.degree. F. (399.degree. C.), for a period of time to solution treat the aluminum-zinc alloy coating overlay, and cooling slowly to at least 350.degree. F. (177.degree. C.).

Abstract: This invention is directed to an improved zinc containing metallic coated ferrous product, particularly sheet and strip, which is resistant to intergranular penetration by zinc and embrittlement of the ferrous base. Use of such zinc containing metallic coated ferrous product in elevated-temperature service, such as found with certain appliances and automotive exhaust components, is enhanced by the coated products of this invention. The resistance to embrittlement of the zinc containing metallic coated ferrous base, when subjected to elevated service temperatures, is achieved by the use of a high-phosphorus containing steel base. For a plain content steel base, a phosphorus content of at least 0.020% by weight, preferably at least 0.030%, and more preferably at least 0.039% was found sufficient to render such zinc-alloy coated ferrous base resistant to embrittlement by zinc.