THE EFFECT OF TEMPERATURE AND pH ON THE CORROSION RATE OF CARBON STEEL in 1 M NaCl

Abstract

An investigation was carried out study the effect of temperature and pH on corrosion rate using carbon steel rotating cylinder electrode in deaerated 1M NaCl solution at pH 3, 6 & 8 and temperatures 25, 50 & 80 C˚ for one hour. It was found that corrosion behavior of carbon steel was greatly influenced by rotation speed at lower pH whereas at higher pH there was a less effect of rotation speed on the corrosion rate and became constant till reached critical speed .The critical speeds in this study were 4000, 3000 & 2000 rpm at 25, 50 & 80 C˚ respectively . This was attributed to the fact that at pH3 the corrosion rate was activation-controlled. At pH3 the corrosion rate was increased from (16.347mpy)50c̊ at static conditions, till reached critical speed, to (88.926mpy)50c̊ due to the formation of protective hydroxide film on the metal surface which restricts access of H2O to the surface .Also study the effect of temperature on corrosion rate by derived mathematical model for experimental data