Production of a zinc-aluminum alloy coating by immersion into molten metal baths

A process for non-continuous galvanization of a metal object with a Zn—Al alloy in a molten Zn—Al alloy bath comprising:

• pre-coating the surface of the metal object with a metallic pre-coating layer so that a uniform, continuous, thin coating of metal is obtained sufficient to protect the surface of the object from oxidation prior to dipping into the galvanization bath, and yet sufficiently thin that the pre-coating can substantially completely react with Al in a molten Zn—Al alloy bath or be substantially completely dissolved in the bath;
• subjecting the pre-coated surface to a surface activation treatment comprising immersing the pre-coated object in a dilute solution of hydrochloric acid, thereby forming on the surface of the pre-coated object a protective layer comprising chloride salt coating having a melting temperature below the temperature of the molten Zn—Al alloy bath, and
• dipping the pre-coated metal having the protective chloride salt coating into a molten Zn—Al alloy bath and controlling the temperature and dipping time such that the chloride salt melts and the pre-coating substantially completely reacts with Al in the bath to form an interface compound layer or substantially completely dissolves in the bath, thereby causing the ZnAl alloy bath to react with the surface of the metal object and form an adherent layer and produce a continuous galvanized coating.