Study On Selection And Corrosion Behavior Of Materials In Coal Gas Condensate

At present, to avoid the corrosion of the equipment for utilization coal gas due to the acid condensate, the temperature of flue gas is commonly over 150℃. As a result, lots of energy is wasted and environmental pollution is serious. To recycle thermal energy, absorb the harmful gas, and realize high efficiently, energy-saving and environmental-friendly, we need reduce the temperature of flue gas. So, the anti-corrosion in gas condensate is one of the key technologies of its research and development.This paper aims at solving the corrosive problem by selecting anti-corrosion material. Ni-Cu-P coating, aluminizing carbon steel and sherardizing carbon steel are primarily researched and compared with each other. Their corrosion-resistance was studied by polarization curve (PC) and electrochemical impedance spectroscopy (EIS) and immersion testing methods. The results showed that in the gas condensate Ni-Cu-P coating the corrosion rate of Ni-Cu-P coating was the least and the electrochemical impendence was biggest. Therefore, it can be used as an anti-corrosionmaterial on condensing heat exchanger.The corrosion behavior of Ni-Cu-P coating in different anions (Cl-, SO42-, NO3-, NO2-) was studied by PC and EIS.The results showed that, in the higher concentration of electrolyte, the corrosion rate of Ni-Cu-P coating was higher in in Na2SO4 and NaCl solution dued to the adsorption of Cl- and SO42-, in the lower concentration of electrolyte, the adsorption of Cl" and SO42- sulfate became weaker, while NO3- adsorption leaded the higher corrosion rate of Ni-Cu-P coating. In addition, as the temperature rose the adsorption of anions became stronger and speeded up the process of coating corrosion. The electrochemical impedance was mainly depended on the formation of surface passivation membrane, and the passivation was caused by the dissolution of Ni.