Surface Modification, Organometallic and Polyaryl Coatings, and Flame SprayTechnologies for Preventing Corrosion of Metals

摘要

To improve adherent properties of electrogalvanized steel (EGS) to polymerictopcoats, the surfaces of EGS were modified by polyelectrolyte-modified zinc phosphating solution. The electrochemical reaction between phosphating solution and EGS led to the complete coverage with fully grown hopeite crystals after only 5 sec treatment, thereby improving adhesion to topcoating and providing protection of EGS against corrosion. To evaluate the ability of polyphenylene sulfide (PPS) coatings to protect zinc phosphate (Zn.Ph)-treated steels from corrosion in a wet, harsh environment, we exposed them in autoclave to attempt heating-cooling cyclic fatigue tests (1 cycle = 12 hr at 200C + 12 hr at 25C) up to 90 times. The major chemical reaction at the interfaces between the PPS and Zn in the Zn.Ph layer during cycling led to the formation of ZnS reaction product, which enhanced the Zn.Ph-to-PPS adhesive bond; correspondingly, there were no signs of peeling and separation of the coating after 90 cycles. Organometallosiloxane polymer (OMSP) was synthesized through the hydrolysis-condensation reaction of the mixed precursor solutions of the N-3-(TRIETHOXYSILY) PROPYL-4,5,-DIHYDROIMIDAZOLE AND B-trimethoxysilylethyl-2-pyridine sols in liquor medium and the metal alkoxides and metallocene dichloride dissolved in water or tetrahydrofurane. The OMSP films (thickness, 0.3 to 1.0 microns) deposited by simple dip-withdrawing coating methods to aluminum alloys displayed the 3000 hr-salt spray resistance. Using a flame spray coating process, the methacrylic acid-modified polyethylene copolymer was overlaid onto cold rolled steel surfaces.