COMBINED COATINGS AGAINST MECHANICAL WEAR AND CORROSION LOW CARBON STEEL

In this study, special ceramic coatings were prepared on low carbon steel (1.0060 - EN 10027-2) via the plasma spraying technique using a WSP (R)-H plasma generator with output of up to 40 kg/h of aluminum oxide. Corundum coatings were deposited directly on the surface of steel plungers equipped with an anti-corrosion interlayer of zinc phosphate. Coating adhesion properties were tested using pin-off tests (modified ISO 4624) and reached a maximum value of 26 MPa. Corrosion resistance was evaluated by measurements of impedance spectra in the 100 kHz - 10 mHz range in a water solution of sodium sulfate. The capacity of electric double-layer varied depending on the porosity and thickness of the coating. Low-porosity coatings of >1.5 mm thickness had R-CT 1.29.10(5) Omega.m(2). The abrasive resistance of coatings was measured by rotary/machining test with SiC cutting knives, using a downforce of 50 kg.cm(-2). Abrasion losses decreased with the quality of finish - starting at 0.00266 g cm(-2) min(-1) down to virtually zero losses after polishing the surface below R-a = 0.55 mu m.