Study the effect of sodium nitrite as a green corrosion inhibitor for the sputter-deposited tungsten-based ternary alloys in 0.5 M NaCl solution

Abstract

Effects of sodium nitrite on the corrosion resistance and mechanism of the sputter-deposited W-80Cr-10Zr and W-42Cr-5Ni alloys were studied using corrosion tests and open circuit potential (OCP) measurements in 0.5 M NaCl solution, open to air at 25ºC. The corrosion resistance property of the W-80Cr-10Zr and W-42Cr-5Ni alloys was enhanced by the use of environmental friendly corrosion inhibitor of sodium nitrite. Higher corrosion resistance property and passivation behavior was observed for the W-42Cr-5Ni alloy than that for the W-80Cr-10Zr alloy based on the corrosion rate and OCP measurements. Adsorption process obeyed Langmuir adsorption isotherm to explain the corrosion inhibition mechanism of the alloys by sodium nitrite solution. The standard free energy change of adsorption of sodium nitrite on the W-80Cr-10Zr and W-42Cr-5Ni alloys was found to be -23.70 KJ/mole and -23.38 KJ/mole, respectively which suggested that sodium nitrite is strongly adsorbed on the surfaces of the alloy surfaces by physical adsorption, not by the chemisorption. As a result the corrosion resistance property of the alloys was significantly increased with increasing the sodium nitrite concentration. From the OCP measurement, it is concluded that sodium nitrite acts as an anodic corrosion inhibitor, because the OCPs of the alloys in presences of the corrosion inhibitors were shifted to more positive direction with increasing the concentration of sodium nitrite in 0.5 M NaCl solution open to air at 25ºC.DOI: http://dx.doi.org/10.3126/bibechana.v12i0.11670BIBECHANA 12 (2015) 1-12