Metal-coated steel strip

A method of forming an Al—Zn—Si—Mg alloy coating on a steel strip having no visual apparent ash mark defect, the method including:

• dipping the steel strip into a bath of molten Al—Zn—Si—Mg alloy containing, in % by weight,
• Zn:
• 30% to 60%
• Si:
• 0.3% to 3%
• Mg:
• more than 1.8% to and less than 3.0%
• Balance:
• Al and unavoidable impurities;
• forming a coating of the alloy on exposed surfaces of the steel strip;
• controlling Ca composition of the molten Al—Zn—Si—Mg alloy in the bath to be at least 100 ppm and less than 200 ppm, and
• controlling the rate of cooling of a coated steel strip after the coated steel strip leaves the bath to be greater than 10° C./s and less than 40° C./s while the coated strip temperature is between 400° C. and 510° C., so that there is a uniform Al/Zn ratio across the surface of the coating formed on the steel strip such that a variation in an Al/Zn ratio between two or more independent areas on a surface of the coating formed on the steel strip is less than 0.1.