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A corrosion-resistant non-crystalline coating was fabricated by plasma electrolytic oxidation (PEO) on Q235 low carbon steel for ship pipes. The distribution and composition of chemical elements and phases of PEO coatings were analyzed by an orthogonal experiment, and the formation mechanism of PEO coatings was discussed. The corrosion current densities and corrosion potentials were measured. The results indicated that the formation of a transition layer mainly containing Fe3O4 was crucial for achieving an excellent coating quality. Furthermore, the corrosion current density of coated steel was reduced by 78% compared with the bare steel.

A surface texture produced by three-step microarc oxidation (MAO) was optimized to improve the tribology performance of a self-lubricating composite coating for diesel engine piston skirts. WS2 was introduced into the self-lubricating composite coating as a self-lubricating additive. The effects of MAO’s varying electrical parameters in terms of stages and action time on the microstructure and chemical composition of the coatings were analyzed by XPS mapping, micron CT, SEM, XRD, and EDS mapping. Furthermore, friction-wear tests under dry lubricating were employed to evaluate the self-lubricating property of the composite coating. Compared to the bare ZL109 aluminum alloy, the optimized composite coating’s friction coefficients were reduced by 60%. Notably, the wear loss of cylinder liner samples matched with the optimized composite coating was almost zero under this work condition.

Ceramic based self-lubricating coating was successfully fabricated on Al-based plasma electrolytic oxidation (PEO) ceramic coating in this work. The coating was reinforced with thermosetting polyimide (PI) containing tungsten disulfide (WS2) fillers. The morphology, chemical composition and phase structure of the PEO, PEO/PI and PEO/PI/WS2 coatings were observed by SEM, EDS and XRD, respectively. Tribological properties of the coatings were comparatively investigated using a reciprocating pin-on-block tribotester under different conditions. Under dry sliding conditions, the friction coefficient of PEO/PI/WS2 coating was about 0.4, which was 50% lower than that of PEO coating. Meanwhile, the wear rate of counter pin cooperated with PEO/PI/WS2 coating was only 0.04 mg min−1, which was 90.9% lower than that of PEO coating. Under step loading conditions, the load was ultimately increased to 70 N and the total duration time was about 35 min, while the corresponding values of PEO coating were 30 N and 13 min, respectively. These are owed to the hard ceramic coating and the soft self-lubricating coating, which can improve the load capacity and decrease the friction, of the ceramic based self-lubricating coating.