THE EFFECT OF CHANGE OF PH ON THE INHIBITORY-ACTION OF 3-(TRIMETHOXYSILYL)PROPANETHIOL-1 ON CORROSION BEHAVIOR OF CARBON-STEEL IN NACL SOLUTIONS

The inhibitory action of 3-(trimethoxysilyl)propanethiol-1 (TMSPT) on carbon steel corrosion in NaCl 3.5% solutions of different pH (2, 6 and 12) at 25-degrees-C and with an initial dissolved oxygen content of 6.5 ppm was examined. Different amounts of TMSPT (0.5 x 10(-3), 1.1 X 10(-3) and 2.7 X 10(-3) mol l-1) were added to NaCl solutions. Electrochemical and weight loss tests show that the inhibitory action of TMSPT increases with increasing TMSPT concentration, and decreases with increasing exposure time, more strongly in solutions at pH 2 and 12 and weakly in solutions at pH 6. At pH 2 and 6 TMSPT acts as both an anodic and cathodic inhibitor, reaching an inhibiting power of 60% at its highest values; at pH 12, TMSPT mainly acts as a cathodic inhibitor, reaching a comparable inhibiting power.