Abstract: A plated aluminum sheet has improved spot weldability and press-formability and is suitable for use in the manufacture of automobile bodies. The aluminum sheet has a plated coating of a metal having a melting point of about 700.degree. C. or above, e.g., Cr, Mn, Fe, Co, or Ni, an alloy of two or more of these metals, or a Zn alloy with at least one of these metals, on one or both surfaces thereof.

Abstract: An aluminum sheet for use in spot welding has an anodic oxide film with a thickness of 50 .mu.m or less on at least one surface thereof. The anodic oxide film is preferably overlaid with a plating layer predominantly comprising at least one metal selected from the group consisting of Zn, Cr, Co, Ni, Fe, and Mn. The aluminum sheet can be produced by subjecting an aluminum or aluminum alloy sheet to anodic oxidation in an acidic solution having a pH of 4 or less conditions of from 2 to 200 V in voltage and from 0.2 to 200 seconds in duration, optionally followed by electroplating in an acidic plating bath.

Abstract: A multilayer plated aluminum sheet suitable for use in automobile body panels comprises a base aluminum sheet made of aluminum or an aluminum alloy and has a first layer of zinc or a zinc alloy formed by displacement plating on the surface of the aluminum sheet and one or more layers of electroplated coating formed on the first layer by electroplating in an acidic bath. Preferably, the upper electroplated coating comprises at least one layer of zinc or a zinc alloy and the uppermost layer of the coating is formed from a metallic material having a melting point above 500.degree. C.

Abstract: A process for zinc electroplating of aluminum strip which can be performed continuously at a high speed and a high current density. The process comprises subjecting aluminum strip to anodic electrolysis in an acidic solution which may be an acidic plating bath solution or a pickling solution before the strip is subjected to cathodic electrolysis in an acidic zinc plating bath to perform zinc electroplating.

Abstract: Steel plate for automobile bodies and a method for manufacturing the steel plate are disclosed, the steel plate containing 0.02.about.0.03% of P as an alloying element with a total amount of Cu, Ni, Cr, and Mo being more than 0. 01% but less than 0.08 weight % and being electroplated with a Zn alloy.

Abstract: A continuous multi-layer plating line for steel sheet which includes a hot-galvanizing apparatus to form a galvanized coating and optionally to alloy the coating and an electroplating apparatus to form an electroplated coating on the galvanized coating. Between the hot-galvanizing apparatus and the electroplating apparatus, a post-galvanizing surface treatment apparatus effective for removing surface oxide contaminants and activating the surface of the galvanized coating is disposed and the galvanized steel sheet is treated thereby prior to electroplating. The post-galvanizing surface treatment may be carried out by applying an alkali solution or an acid which can dissolve aluminum oxide to the galvanized coating, by alkali electrolysis, by cathodic electrolysis, by cooling the galvanized steel sheet with an alkali solution, or by skin-pass rolling using an alkali solution or an acid which can dissolve aluminum oxide as a skin-pass roling liquid.

Abstract: A process for direct zinc electroplating of aluminum strip which can be performed continuously at a high speed and a high current density. The process comprises pretreating aluminum strip by alkaline degreasing and then pickling and subjecting the pretreated aluminum strip to zinc electroplating in an acidic zinc plating bath which contains, in addition to Zn.sup.2+ ions, metal ions selected from the group consisting of Ni.sup.2+ ions and Fe.sup.2+ ions in a concentration of at least about 10 g/1 to form a Zn-Ni, Zn-Fe, or Zn-Ni-Fe alloy plated coating, which may be overlaid with another zinc electroplated coating.

Abstract: Steel plate for automobile bodies and a method for manufacturing the steel plate are disclosed, the steel plate containing 0.02.about.0.03% of P as an alloying element with a total amount of Cu, Ni, Cr, and Mo being more than 0.01% but less than 0.08 weight % and being electroplated with a Zn alloy.

Abstract: A corrosion resistant duplex plated sheet steel is disclosed, which comprises a sheet steel having on at least one surface thereof a lower layer of Zn base alloy plating and an upper layer thereon selected from a zinc plating having a coating weight of 0.1-5 g/m.sup.2 and a zinc alloy or zinc composite plating having a coating weight of 0.1-10 g/m.sup.2. The ratio of the coating weight of the lower layer to that of the upper layer is at least 1:1 and in the case of upper layer of zinc alloy or zinc composite plating, it comprises, on a weight basis as metal, at least 80% Zn, and one or more additives as Zn corrosion inhibitors selected from Ni, Co, Mn, Sn, Ti, Al, Mg and Si. The duplex plated sheet steel is suitable for coating thereon with an electrophoretic coating composition and exhibits excellent cratering resistance in cathodic electrophoretic coating and excellent cosmetic resistance after painting.