Rust converter

Abstract: Pretreatment of reinforcement steel surface with tannic acid based rust converter (RC) prior to the application of zinc rich coating (ZRC) is observed to improve its corrosion resistance appreciably. This improvement is caused due to decrease of pH of the corroding interface as a result of outward diffusion of acidic components of RC from the converted rust layer. The decrease in pH of corroding interface brings the ZRC in the protective pH range of Zinc and accelerates the formation of passive layer. This layer is identified as Hydrozincite (HZ). Electrochemical Impedance Spectroscopy (EIS), Potential-time studies, Raman Spectroscopy, Scanning electron Microscopy (SEM), energy dispersive X-ray analysis (EDXA) and X-ray diffraction studies have been performed to understand the mechanism and kinetics of the film formation.

Abstract: Rust converters are chemical formulations that can be applied to corroded surfaces to convert residual rust on iron/steel surfaces into harmless and adherent chemical compounds. The known hazardous effects of most synthetic rust converters have led to a search for safer, more environmentally friendly natural products. Tannins, a class of natural, non-toxic and biodegradable polyphenolic compounds, extracted from plant sources have been proposed as an alternative. The transformation of rust in the presence of 5 g L−1 tannins extracted from mangrove (Rhizophora apiculata) barks was studied. Three different methods of pre-rusted sample preparations were tested. The rust composition of the steel was dependent of sample preparation. The pre-rusted samples prepared formed predominantly lepidocrocite and magnetite. Transformation of rust components to ferric-tannates, particularly lepidocrocite, in the presence of mangrove tannins that could be observed via Fourier transform infrared spectroscopy, X-ray ...