Structural, Micromechanical and Tribological Characterization of Zn–Ni Coatings: Effect of Sulfate Bath Composition

International audienceZn and Zn-Ni alloy coatings were electrode-posited on mild steel from sulfate-based bath containing Sn as additive. The effect of Ni content on the microstructure, morphology, micro hardness and the tribological behavior of these coatings were studied and discussed. Adding Sn in the sulfate bath had a significant effect on the surface morphology, particularly on the Zn-8 wt% Ni coatings. By increasing the Ni concentration from 8 to 14 wt%, the X-ray patterns showed that the phase structure of Zn-Ni alloy coatings was changed from g-phase Ni 3 Zn 22 to c-phase Ni 5 Zn 21. The plastic deformation and delamination were found to be wear mechanisms for the investigated coatings. While the Zn-14 wt% Ni alloys had the best wear resistance, Zn films had the most severe wear volume loss and the highest friction coefficient

Corrosion of titanium: Part 1: Aggressive environments and main forms of degradation

Titanium has outstanding corrosion resistance due to the external natural oxide protective layer formed when it is exposed to an aerated environment. Despite this, titanium may suffer different forms of corrosion in severe environments: uniform corrosion, pitting and crevice corrosion, hydrogen embrittlement, stress-corrosion cracking, fretting corrosion and erosion. In this first review, forms of corrosion affecting titanium are analyzed based on a wide literature review. For each form of corrosion, the mechanism and most severe environment are reported according to the current understanding. In the second part, this review will address the possible surface treatments that can increase corrosion resistance on commercially pure titanium: Electrochemical anodizing, thermal oxidation, chemical oxidation and bulk treatments such as alloying will be considered, highlighting the advantages of each technique