Protective coating processes for zinc coated steel

A process for protectively coating a surface of zinc coated or zinc alloy coated steel, said process comprising the steps of:

• (A) contacting the predominantly zinc surface with a composition effective for activating said predominantly zinc surface for phosphating for a time effective for activating;
• (B) forming over the surface activated in step (A), within a time not greater than 10 seconds, a phosphate conversion coating consisting predominantly of zinc phosphate and containing at least 3% by weight manganese, by contacting the surface activated in step (A) with a composition consisting essentially of water and:
• Total Phosphate:
• 5-20 g/L
• Zn.sup.+2 :
• 1.0-5.0 g/L
• Mn.sup.+2 :
• 0.5-3.0 g/L
• Ni.sup.+2 :
• 0.5-3.0 g/L
• Iron cations:
• 0.0-0.5 g/L
• Simple Fluoride:
• 0.0-1 g/L
• Complex Fluoride:
• 0.1-7 g/L
• "Accelerator":
• 2-10 g/L
• (C) posttreating the conversion coating formed in step (B) by contact for a sufficient time with a posttreating composition;
• and
• (D) surface coating the posttreated conversion coated surface formed in step (C) with a coating at least 10 .mu.m thick of material selected from the group consisting of polyester polymers, fluoropolymers that are predominantly poly(vinylidene fluoride), siliconized polyester polymers, copolymers of epoxy resins and hardeners for such resins, and materials that are predominantly poly(vinyl chloride) ("PVC").