Anti corrosive electroless Ni-P films for mild steel materials

摘要

Purpose - The purpose of this paper is to evaluate the corrosion resistance of the electroless Ni-P coatings in two aggressive media 3.5 wt.% NaCl and Synthetic industrial waste water. Also to study the effect of Phosphorous content in the electroless Ni-P deposits on its surface nature, morphology and corrosion resistance. Design/methodology/approach - The corrosion behavior of electroless Ni-P coatings generated on mild steel coupons from an acidic and an alkaline baths and their anti-corrosion performance of was compared systematically in 3.5 wt.% of NaCl solution and also in synthetic industrial waste water. Microstructure and surface composition of coatings were analyzed using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy techniques, respectively. The Ni-P coated mild steel specimens were subjected to corrosion and the rate of corrosion was studied by chemical and electrochemical methods. The linear sweep voltammetry, Tafel and electrochemical impedance spectroscopy were employed to obtain corrosion data. Findings - The electroless Ni-P coatings with higher P content possess homogeneous, uniform and amorphous surface nature and exhibited higher corrosion resistance in the aggressive corrosive media chosen. Originality/value - This paper provides corrosion behavior of electroless Ni-P coatings in 3.5 wt.% NaCl and synthetic industrial waste water, and establishes the importance of phosphorous content on nature and properties of the coatings.