Abstract
High strength low alloy (HSLA) steels exhibit many outstanding properties for industrial applications but suffer from unsatisfactory corrosion resistance in the presence of aggressive chlorides. Phosphate coatings are widely used on the surface of steels to improve their corrosion properties. This paper evaluates the effect of a manganese phosphate coating prepared after various mechanical surface treatments on the electrochemical corrosion characteristics of S355J2 steel in 0.1 M NaCl electrolyte simulating aggressive sea atmosphere. The manganese phosphate coating was created in a solution containing H3PO4, MnO2, dissolved low carbon steel wool, and demineralised H2O. Scanning electron microscopy (SEM) was used for surface morphology observation supported by energy-dispersive X-ray analysis (EDX). The electrochemical corrosion characteristics were assessed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PD) measurements in the solution of 0.1 M NaCl. Method of equivalent circuits and Tafel-extrapolation were used for the analysis of the obtained results. Performed experiments and analysis showed that the morphological and corrosion properties of the surface with manganese phosphate are negatively influenced by sandblasting surface pretreatment.
Highlights
The prime motivation of developing high strength low alloy (HSLA) steels was the replacement of low-carbon steels for the automotive industry in order to improve their strength-to-weight ratio and meet the need for higher-strength construction grade materials
The present work describes the influence of various surface treatments on morphological and corrosion properties of manganese phosphate on S355J2 steel
Using the manganese phosphating process created a continuous coating on the steel surface after both mechanical surface pretreatment techniques
Summary
The prime motivation of developing high strength low alloy (HSLA) steels was the replacement of low-carbon steels for the automotive industry in order to improve their strength-to-weight ratio and meet the need for higher-strength construction grade materials. Proper surface treatment is necessary for many applications to increase their resistance to aggressive environment. One of the most commonly used method for surface preparation is sandblasting, used for various purposes of surface influence including: modification [2], strengthening [3], cleaning and rust removal [4]. Sandblasting abrasive particles are smaller compared with particles in shot peening technology and lower pressure of compressed air is used. A smoother surface can be Coatings 2016, 6, 46; doi:10.3390/coatings6040046 www.mdpi.com/journal/coatings
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