SURFACE TREATMENT CHEMICALS AND BATH FOR ALUMINUM OR ITS ALLOY AND SURFACE TREATMENT METHOD

摘要

A surface treatment chemical composition for aluminum or its alloys 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 composition 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 surface treatment using this bath.