Abstract: A surface treatment chemicals for aluminum or its alloy consisting essentially of 10-1000 parts by weight of niobium ion and/or tantalum ion, and 1-50 parts by weight of effective fluorine ion, and optionally 10-500 parts by weight of zirconium ion and/or titanium ion and 10-500 parts by weight of phosphate ion. A surface treatment bath is produced by diluting the surface treatment chemicals so as to have a pH of 1.5-4.0. Excellent resistance to blackening by boiling water and adhesion to an overlying polymer coating film can be obtained by a surface treatment using this bath.

Abstract: A surface treatment chemicals for aluminum or its alloy consisting essentially of 10-1000 parts by weight of niobium ion and/or tantalum ion, and 1-50 parts by weight of effective fluorine ion, and optionally 10-500 parts by weight of zirconium ion and/or titanium ion and 10-500 parts by weight of phosphate ion. A surface treatment bath is produced by diluting the surface treatment chemicals so as to have a pH of 1.5-4.0. Excellent resistance to blackening by boiling water and adhesion to an overlying polymer coating film can be obtained by a surface treatment using this bath.

Abstract: A cleaning agent is used to wash surfaces of aluminum products in a cleaning bath. The cleaning agent is a water-soluble acid containing ferric ions. During the cleaning process, the ferric ions are reduced to ferrous ions. The used cleaning agent is sent to an electrolytic tank so that the ferrous ions are subject to the electrolytic oxidation to be converted into ferric ions. The regenerated cleaning agent is returned to the cleaning bath.

Abstract: A surface treatment chemical for aluminum or its alloy consisting essentially of 10-1000 parts by weight of one or more ions of metals selected from the group consisting of scandium, yttrium, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, 10-500 parts by weight of zirconium ion, 10-500 parts by weight of phosphate ion and 1-50 parts by weight of effective fluorine ion. A surface treatment bath for aluminum or its alloy consisting essentially of 10-1000 ppm of one or more ions of metals selected from the group consisting of scandium, yttrium, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, yttterbium and lutetium, 10-500 ppm of zirconium ion, 10-500 ppm of phosphate ion and 1-50 ppm of effective fluorine ion, and having a pH of 1.8-4.0.

Abstract: A hydrophilic surface treatment chemicals comprising, on a solid basis,(a) 1-10 parts by weight of at least partially saponified polyvinyl acetate having a saponification degree of 45 or more and a polymerization degree of 100-600,(b) 0.3-15 parts by weight of water-soluble nylon, and(c) 0.1-5 parts by weight of a water-soluble amino resin,a weight ratio of the component (b) to the total of the components (a) and (c), (b)/[(a)+(c)], being in the range of 1-1/4, and a weight ratio of the component (a) to the component (c), (a)/(c), being in the range of 1/0.05-1/0.5. The hydrophilic surface treatment bath is prepared by properly diluting the chemicals for surface-treating aluminum members.