Effects of pH Variation on Corrosion of Mild Steel in Bore-hole Water using 1M Sodium Hydroxide Solution

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Author(s) S.I. Durowaye | A.G.F Alabi | O.I. Sekunowo | B. Bolasodun | I.O. Rufai
Pages 139-144
Volume 4
Issue 3
Date March, 2014
Keywords Mild Steel, Bore-hole water, NaOH, Corrosion, pH, Conductivity, Optical Emission Spectrometer.

Abstract

Corrosion of metals is a major industrial problem that has attracted a lot of investigators in recent years and huge financial losses are always incurred by the replacement of corroded parts. The corrosion of mild steel in bore-hole water of different pH values of 7.20, 8.20, 9.20, 10.20 and 11.20 using 1M sodium hydroxide (NaOH) solution at room temperature was investigated by chemical technique. The specimen in bore-hole water of pH value 11.20 has the least corrosion rate of 8.650 mpy while the one in bore-hole water of pH 7.20 has the highest value of 12.974mpy. It is shown that there is a progressive decrease in both conductivity and rate of corrosion product formation on the test specimens from the solutions as the pH increases from 7.20 to 11.20. This is due to that fact that sodium hydroxide supplies hydroxyl ions OH¬– which possibly absorb to the surface of the specimen by acting as an anodic inhibitor which increases anodic polarisation by helping to form a protective film and keeps it repaired thereby retarding or reducing the rate of corrosion as the pH increases.

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