Method for providing a Zn—Al—Mg coating, and such coating

A steel strip having a Zn—Al—Mg coating provided by hot dip coating, wherein the coating has a composition consisting of:

• 1.1-1.4 weight % magnesium;
• 1.9-2.3 weight % aluminium;
• optional <0.3 weight % of Sn, Bi, Sb, Ln, Ce, Ti, Sc, Sr and/or B in total;
• the remainder consisting of zinc and unavoidable impurities;
• wherein the Al and Mg contents satisfy the relationship:
• Al (in weight %) >1.28 Mg (in weight %)+0.25 with the proviso that if Al is 2.0 weight % then Mg may be 1.4 weight %,
• wherein the coating weight of a one-sided coating layer is 35 to less than 45 g/m2, and
• wherein the coating does not contain binary (Zn+MgZn2) microstructures,
• wherein the coating has an absence of a visible beach defect;
• wherein the strip has a roughness Ra<1.5 μm before entering a coating bath for the hot dip coating,
• wherein the coated steel strip is made by a process comprising controlling the thickness of the coating using gas knifes above a coating bath that provides the alloy for the coating and wherein Z is a value in a range of 5 to 8 mm that meets an equation Z<0.6 e0.064CW, wherein Z is the distance between each gas knife and the steel strip in mm, and wherein CW is the weight of the one-sided coating layer in g/m2 and wherein each said gas knife has a distance above the coating bath of at most 500 mm.