Abstract: An object of this invention is to provide a copper-tin alloy plating bath that allows for film thickening without using cyanide ions, and that can also be applied to barrel plating. This invention relates to a copper-tin alloy plating bath comprising an aqueous solution containing a water-soluble copper compound, a water-soluble divalent tin compound, a sulfur-containing compound represented by formula (1): R—(CH2)l—S—(CH2)m—S—(CH2)n—R??(1), wherein R is H, OH, or SO3Na, and l, m, and n are each independently an integer of 0 to 3, and a hydroxyl group-containing aromatic compound.

Abstract: An object of the present invention is to provide multilayer plating film with excellent corrosion resistance. The present invention provides a multilayer plating film containing at least a chrome plating film and a tin-nickel plating film, the chrome plating film being the outermost layer, and the tin-nickel plating film being formed below the chrome plating film by using an acidic tin-nickel alloy plating solution containing a divalent tin compound, a nickel compound, a triamine compound, and a fluoride.