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 considerable
corrosion damages of metals. This is due to free corrosion effect or the formation of
concentration cell of pollutants resulting in a galvanic effect. The current work was devoted
to study the effect of formic acid (CH2O2) as an organic pollutant on the corrosion rate of
carbon steel under different operating conditions. It includes an investigation of galvanic
corrosion caused by the establishment of concentration cell of formic acid under different
operating conditions. The ranges of operating parameters were formic acid concentration of
10-4 - 10-5 M and temperature of 32 - 50 °C. The results showed that increasing formic acid
concentration to 10-4 M leads to an increase in the corrosion rate by up to 7.6 times that in
the water of 0.1N NaCl. In addition, the corrosion rate in each terminal in concentration
cell also increased by up to 2.3 times. Pumping of air in formic acid solution led to a
considerable increase in the corrosion rates and enhances the concentration cell effect
which increases the galvanic currents. High increase of corrosion rate was noticed by
pumping the air at high temperature reaching up to 4 times depending on temperature. In
general, the galvanic currents were high initially and decreased with time due to the
formation of corrosion product layer. The increase in temperature from 25 to 50 oC caused
an increase in the galvanic corrosion rate reached up to 2 times in formic acid solution. In
addition, the galvanic currents were noticed to decrease with temperature while the
corrosion rate of each terminal was increased.