Abstract

Fe-600 grade steels are recommended for high rises and other structures in India that require high-load carrying capacity (particularly in seismic zones) due to its excellent mechanical properties. But structures in food processing, agricultural waste handling, etc., industries and high rises are subjected to attack of sulphates as well as acid rain. The present work investigates the efficacy of electroless nickel coatings in corrosion prevention of Fe-600 grade rebars exposed to aggressive sulphate environment. Ni-P, Ni-P-W and Ni-P-Cu coatings were deposited on the rebars. Electrochemical tests such as potentiodynamic polarization and electrochemical impedance spectroscopy were employed to investigate the corrosion behaviour in 0.5 M sulphuric acid. It was seen that corrosion potential of rebars was nobler when they were coated with electroless nickel ternary variant coatings. Electrochemical impedance spectra also validated the same. Scanning electron microscope images of the surface of the bare rebars post electrochemical tests revealed a completely cracked morphology due to severe attack of sulphates. Whereas the surface of Ni-P-W coated rebar revealed the least damage and highest corrosion resistance.

摘要

Fe-600 级钢推荐用于印度的高层建筑和其他需要高承载能力（特别是在地震区）的结构，因为它具有出色的机械性能。但食品加工、农业废物处理等、工业和高层建筑的结构受到硫酸盐和酸雨的侵蚀。目前的工作研究化学镀镍涂层对暴露于腐蚀性硫酸盐环境的 Fe-600 级钢筋的防腐效果。Ni-P、Ni-PW 和 Ni-P-Cu 涂层沉积在钢筋上。电化学测试如动电位极化和电化学阻抗谱被用来研究在 0.5 M 硫酸中的腐蚀行为。可以看出，当钢筋涂有化学镀镍三元变体涂层时，它们的腐蚀电位更高。电化学阻抗谱也证实了这一点。电化学测试后裸钢筋表面的扫描电子显微镜图像显示，由于硫酸盐的严重侵蚀，其形态完全破裂。而 Ni-PW 涂层钢筋的表面显示出最小的损坏和最高的耐腐蚀性。