The present invention provides an improved aqueous alkaline zincate solution comprising hydroxide ions, zinc ions, nickel ions and/or cobalt iron ions, copper ions, and at least one inhibitor containing one or more nitrogen atoms, sulfur atoms, or both nitrogen and sulfur atoms provided said nitrogen atoms are not present in an aliphatic amine or hydroxylamine. The present invention also relates to methods for depositing zincate coatings on aluminum and aluminum alloys comprising applying an immersion zincate coating on an aluminum or aluminum alloy substrates, optionally followed by plating the zincate coated aluminum or aluminum alloy substrate using an electroless or electrolytic metal plating solution.