FIELD: chemistry.
SUBSTANCE: agent used with water as a solvent and containing at least one of zirconium, titanium and hafnium, a fluorine element and a co-condensate of silane coupling agent (A) and silane coupling agent (B), where the silane coupling agent (A) is a silane coupling agent having both a tri- or di-alkoxysilane group and an amino group, and the silane coupling agent (B) is characterized by the following general formula : 
, wherein R is one selected from the group consisting of alkylene groups having 1-5 carbon atoms, alkyleneoxy groups having 1-5 carbon atoms and an oxygen atom, Z is a 3,4-epoxycyclohexyl group, a, b and c each is an integer of 0 to 3, provided that the sum of a, b and c is 3 and the sum of a and b is from 2 to 3, and x is an integer of 1 to 3. The said co-condensate is obtained by polymerization of a mixture of the silane coupling agent (A) and the silane coupling agent (B) at ((A):(B)) weight ratio in the range of 1:9 to 18:1, and the mixture of silane coupling agent (A) and silane coupling agent (B) is introduced into an aqueous solvent, and the resulting liquid reaction mixture is subjected to hydrolytic condensation to a degree of condensation of 50% or higher. At that, the fluorine element is partially present in the chemical conversion treatment agent in the form of free fluoride ions, and the content of free fluorine ions is 0.01-100 mg/l.
EFFECT: proposed chemical conversion treatment agent is able to impart a sufficiently high level of adhesion to the surface with the covering film.
6 cl, 3 tbl, 30 ex
