Nippon Steel Corporation

Yukimasa Suemitsu

Motohiro Nakayama

Tatsuya Kanamaru

Ryoichi Naka

Hiroo Goshi

Kazutsugu Nakajima

Yukio Numakura

Hisao Hayashi

Tadafumi Honda

A galvannealed steel sheet having distinguished anti-powdering property and anti-flaking property is disclosed. The steel sheet comprises a matrix steel sheet and a galvannealed coating layer having a coating weight of 45 to 90 g/m.sup.2, composed of 8.about.12 wt. % Fe and 0.05.about.0.35 wt. %, preferably 0.05.about.0.30 wt. % Al, the balance being Zn, provided on at least one side of the matrix steel sheet, the galvannealed coating layer having a .GAMMA. phase with a thickness of not more than 1.3 .mu.m, preferably not more than 1.0 .mu.m in the region at the boundary to the matrix steel sheet, and the surface region of galvannealed coating layer has a structure either (1) .eta. and .zeta. phases do not exist in the surface region of the galvannealed coating layer, or, (2) when at least one of .eta. and .zeta. phases exist therein, the total amount of the at least one of .eta. and .zeta. phases in the galvannealed coating layer is not more than 1.5 g/m.sup.2.

Galvannealed steel sheet with distinguished anti-powdering and

In a process for electrolytically removing metal deposit from a non-plated surface of a single surface-plated metal strip, by bringing, within an electrolytic liquid, a single surface-plated metal strip which serves as an anode plate, into a location at which the non-plated surface of the anode single surface-plated metal strip faces in parallel to and is spaced from a cathode plate, and by applying a principal voltage between the anode metal strip and said cathode plate to electrolytically remove metal deposit from the non-plated surface; whereby undesirable stripping of portions of the plated metal layer in side edge portions of the plated surface of the metal strip is prevented by arranging supplementary anode plates within the electrolytic liquid in such a manner that the supplementary anode plates face in parallel to and are spaced from side edge portions of the plated surface of the anode metal strip, and then, while the principal voltage is applied between the anode metal strip and the cathode plate, a supplementary voltage is applied between the supplementary anode plates and the metal strip, the electric potential of each supplementary anode plate being higher than that of the metal strip.

Process for electrolytically removing metal deposit from a non-plated

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Aichi, Japan

Yukimasa Suemitsu