In-Situ Phosphatizing Coatings II: A High-Solids Polyester Baking Enamel

By Tao Yu, Chhiu-Tsu Lin

A single step in-situ phosphatizing coating (ISPC) can be formulated by pre-dispersing an optimal amount of in-situ phosphatizing reagents (ISPRs) into the paint system. The technique of ISPC is applied to a high-solids polyester-malemine baking enamel using a designed “ISPR-2.”

The in-can stability of ISPC is verified using rheological measurements. The coat-ing properties and protective performance of the ISPC are compared to those of the multi-step coating of control sample (MCCS). The immersion tests in a 3% NaCl solution and salt spray testings show a significant improvement in paint disbondment from the “X” scribe for ISPC.

The observed coating performance enhancement of ISPC over MCCS is confirmed from the multi-functionality of ISPRs. Phosphate chemistry proceeds via an acid-base type of interaction, P-O–— Mn+, and polymer chemistry generates a covalent P-O-C linkage with the polymer net-work.