Corrosion of carbon steel in formic acid as an organic pollutant under the influence of concentration cell

Abstract

The presence of contaminants in water even in small amounts can cause considerablecorrosion damages of metals. This is due to free corrosion effect or the formation ofconcentration cell of pollutants resulting in a galvanic effect. The current work was devotedto study the effect of formic acid (CH2O2) as an organic pollutant on the corrosion rate ofcarbon steel under different operating conditions. It includes an investigation of galvaniccorrosion caused by the establishment of concentration cell of formic acid under differentoperating conditions. The ranges of operating parameters were formic acid concentration of10-4 - 10-5 M and temperature of 32 - 50 °C. The results showed that increasing formic acidconcentration to 10-4 M leads to an increase in the corrosion rate by up to 7.6 times that inthe water of 0.1N NaCl. In addition, the corrosion rate in each terminal in concentrationcell also increased by up to 2.3 times. Pumping of air in formic acid solution led to aconsiderable increase in the corrosion rates and enhances the concentration cell effectwhich increases the galvanic currents. High increase of corrosion rate was noticed bypumping the air at high temperature reaching up to 4 times depending on temperature. Ingeneral, the galvanic currents were high initially and decreased with time due to theformation of corrosion product layer. The increase in temperature from 25 to 50 oC causedan increase in the galvanic corrosion rate reached up to 2 times in formic acid solution. Inaddition, the galvanic currents were noticed to decrease with temperature while thecorrosion rate of each terminal was increased.