Patent ID: 8840968

Claim:
A method of controlling surface defects in a coating on a steel strip comprising the steps of: heat treating a steel strip in a heat treatment furnace; forming a molten bath of a coating alloy for coating the steel strip, the coating alloy being an aluminum-zinc-silicon-magnesium alloy having 50% to 60% aluminum, 37% to 46% zinc, and 1.2% to 2.3% silicon, and a controlled concentration of (i) strontium, or (ii) strontium and calcium of greater than 10 ppm and not more than 150 ppm, where strontium is at least 2 ppm; and hot-dip coating the steel strip in the molten bath to form a coating alloy on the steel strip containing a concentration of (i) strontium or (ii) strontium and calcium resulting from the controlled concentration in the molten bath, wherein spangles on the coating alloy are less than 0.5 mm in a major dimension of the spangles across a surface of the steel strip.