Accession Number : ADA331027

Title :   Interfaces of High-Protection Performance Polyaryls-Coated Zinc Phosphated Steels, Tri-Service Committee on Corrosion Proceedings

Descriptive Note : Conference proceedings

Corporate Author : BROOKHAVEN NATIONAL LAB UPTON NY DEPT OF APPLIED SCIENCE

Personal Author(s) : Sugama, Toshifumi

PDF Url : ADA331027

Report Date : JUN 1994

Pagination or Media Count : 13

Abstract : To evaluate the ability of polyaryl thermoplastic coatings such as Polyphenylenesulfide (PPS) and polyphenyletheretheretherketone (PEEK), to protect zinc phosphate (Zn.Ph)-treated steels from corrosion in a wet, harsh environment (1.0 wt% H2SO4, 3.0 wt% NaCl and 96.0 wt% water at temperature from 25 to 200 deg C), we exposed them in autoclave to measure their performance in heating-cooling cyclic fatigue tests (1 cycle = 12 hr at 200 deg C + 12 hr at 25 deg C) for up to 90 cycles. Although no changes in appearance were seen in the PEEK specimens after 60 cycles, extension to 90 cycles caused delamination of the coating film from the Zn.Ph; the major reason was the degradation of the PEEK polymer caused by its hydrothermal-catalyzed esterification. In urea hydrogen peroxide (UHP) modified PPS-coating systems, chemical reactions at the interfaces between the PPS and Zn in the Zn.Ph layer led to the formation of a ZnS reaction product, which enhanced the Zn.Ph-to-PPS adhesive bond; correspondingly, there were no signs of peeling nor separation of the coating after 90 cycles. In addition, because these intermediate reaction products are insoluble at high pH, they minimized the rate of delamination of the PPS coating caused by the cathodic reaction, H2O + 1/202 + 2e right arrow 2OH(-), at the corrosion side of a defect in the film. In contrast, PEEK coatings containing non-reactive Zn.Ph Underwent cathodic delamination because of the susceptibility of Zn.Ph to alkali dissolution.

Descriptors :   *CORROSION INHIBITION, *PROTECTIVE COATINGS, *THERMOPLASTIC RESINS, STEEL, ETHERS, DELAMINATION, OXIDATION REDUCTION REACTIONS, CYCLIC TESTS, PHOSPHATES, KETONES, POLYPHENYLENES, ZINC COMPOUNDS.

Subject Categories : Coatings, Colorants and Finishes
      Polymer Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE