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Purpose: This study aims to enhance to corrosion protection of NiZn-plated steel by electroplating multilayer coating. Design/methodology/approach: The multilayer coating consists of three layers on mild steel substrate, such as Cr3+ chromate conversion layer (CCC), electrodeposited nanosilica zinc-nickel composite layer (ZnNiSi) and electrodeposited zinc-nickel alloy layer (ZnNi). Its morphology, composition and corrosion behaviour were investigated by various methods. Findings: Polarization curves indicated that polarization resistance and corrosion current density of CCC/ZnNiSi/ZnNi/Fe (6.956 kO.cm2; 2.56 µA.cm−2) were two times higher and five times lower than that of ZnNiSi/ZnNi/Fe (3.42 kO.cm2; 12.52 µA.cm−2), respectively. From electrochemical impedance spectroscopy data, charge transfer resistances were 1.344, 2.550 and 2.312 kO.cm2 for ZnNi, ZnNiSi/ZnNi and CCC/ZnNiSi/ZnNi, respectively. Salt spray test indicated that after 48 h, surface of ZnNi and ZnNiSi was covered by white rust, whereas no white rust was observed on surface of CCC/ZnNiSi/ZnNi. After 600 h, there were red rust spots (1% surface coverage) on surface of Zn-Ni, whereas only white rust was observed on both ZnNiSi/ZnNi (100% surface coverage) and CCC/ZnNiSi/ZnNi (10% surface coverage). Originality/value: Multilayer coating enhanced significantly the corrosion protection for steel, as compared to the single-layer coating. [ABSTRACT FROM AUTHOR]

In the manufacturing industry, the suface for high quality and gloss are often processed by semi - finishing and finishing on the grinding machine after roughing or heat treatment. To improve machining accuracy, to increase labour productivity and product quality, it depends very much on the opertiong status and accuracy of the machine. Therefore, the article has introduced the solution for automation feed motion on a flat grinding machine base on mechanical system of machine, that can automatically control the machining process and integrated of programming to process gringding details with complex frofiles, improve the accuracy of the machine. The research results are carried out on the active real flat grinding products, high quality surface grinding, reducing pocessing time and improving effect opertating of the machine. [ABSTRACT FROM AUTHOR]