Abstract: The invention aims to provide a rare earth metal-based permanent magnet which has on the surface an inexpensive corrosion-resistant film combining excellent heat-resistance with excellent adhesiveness; a process for producing the permanent magnet; and a treating liquid for forming the corrosion-resistant film. The invention provides a rare earth metal-based permanent magnet characterized by it has on the surface a corrosion-resistant film containing lithium silicate and a thermoplastic resin as the constituting components, the film containing uniformly dispersed therein the thermoplastic resin at a content of 0.1 wt % to 50 wt %. The treating liquid, which is an excellent liquid for forming the corrosion-resistant film, is characterized by that a soap-free aqueous emulsion of a thermoplastic resin was used and that it contains the thermoplastic resin and lithium silicate in given amounts.

Abstract: A Zn-Ni alloy electroplated steel sheet exhibiting improved corrosion resistance as well as improved adhesion upon impact and resistance to powdering and a manufacturing process therefor are disclosed. The electroplated steel sheet comprises a steel sheet; a thin Zn-Ni alloy electroplated underlayer on at least one side of the steel sheet in which microcracks having a width of 0.01-0.5 .mu.m and covering 10-60% of the surface area of the electrolplated layer are randomly oriented; and a Zn-Ni alloy electroplated toplayer. The underlayer is prepared by dipping the initially electroplated sheet into an acidic solution containing 20 g/l or more of Ni.sup.2+ and 20 g/l or more of Zn.sup.2+ with a ratio of Ni.sup.2+ /Zn.sup.2+ of 1.0.about.4.0 at a bath temperature of 40.about.70.degree. C. for a period of time (T, seconds) of (5.about.20) .times.W (W: weight of electroplated layer in g/m.sup.2) without applying an electric current to form an Ni-rich pretreated underlayer.