Abstract: In the hot-dip coating utilizing molten metals in which the partial pressure of the metal vapor is substantial at the coating temperature, the resultant metal vapor in the snout area over the metal bath tends to cause pinhole type imperfections on the resultant coating. For example, substantial vaporization occurs during high temperature galvanizing and during hot-dip coating of Al-Zn, in which Al is a major constituent, such that the bath must be maintained at a high enough temperature to keep the aluminum molten. The accumulation of such vapors inside the snout area is minimized by (i) utilizing baffles within the snout to isolate it as much as possible from the cooling section of the annealing furnace, and (ii) venting a portion of the gas from the snout.

Abstract: Hot-dip coated steel articles having a coating containing about 55% aluminum, 43% zinc, 2% silicon, are known to exhibit an optimum combination of general corrosion resistance, more durable than zinc coatings; while providing more galvanic protection to cut edges and areas of mechanical damage than hot-dip aluminum coatings. It has now been found that coatings containing 12 to 24% zinc, up to 4% silicon, balance aluminum, provide galvanic protection equal to or superior to such known coatings, while providing enhanced general corrosion resistance, approaching that of aluminum coatings.

Abstract: A gas knife process for controlling the thickness profile of hot-dip aluminum coatings, employs a hybrid gas knife design incorporating both a "curved-lip" with a "bow-tie" orifice. This design, in combination with very close knife to strip distance at the strip edges, was found to provide desirable coating profiles. Best results are obtained with knife deflections of 5.degree. to 30.degree. below the horizontal while utilizing orifice pressures of 15 to 70 mm of Hg at line speeds of 20 to 150 m/min.