Study On The Corrosion Performance Of A Kind Of Cr-Al Alloying Steel

The alloy composion was screened out though researching corrosion property of Cr-Al alloying J55steel and Cr-Al alloying influenced on the corrosion performance of CT80steel. Three types of corrosion resistant steel made by stove and CT80steel were the test materials. Electrochemical methods、immersion test、autoclave test and SEM、EDS were used to study corrosion behavior of Cr-Al alloy steel, then analyzed the corrosion mechanism compared with CT80steel.The results of electrochemical test showed that relatived CT80steel, open circuit potential of Cr-Al alloy steel shifted to the positive directionobviously; the corrosion current density significantly decreased; Nyquist diagrams presented one time constant and the polarization resistance were greater than CT80steel. The corrosion tendency of Cr-Al alloy steel decreased and the corrosion rate significantly lower than CT80(about lower50%). With the extension of test time, the Nyquist graph has two time constant, and the corrosion product film exhibited higher corrosion resistance than CT80steel.Corrosion weightless test obtained that the Cr-Al alloy steel and CT80characterized by uniform corrosion and the corrosion rate of Cr-Al allov steel was lower that CT80steel (about lower50%) in3.5wt.%NaCl with saturated CO2at60℃. The corrosion of Cr-Al alloy steel and CT80steel has the same trend in3.5wt.%NaCl with saturated H2S at60℃and room temperature. The Cr-Al alloy steel showed a high pitting resistance in3.5wt.%NaCl at room temperature. The corrosion behavior measured by corrosion weightlessness tests was accorded with the electrochemical test.Corrosion mechanism analysis reached that relative to CT80steel, the Cr-Al alloy steel has a larger anode charge transfer coefficient, and the anode polarization is restrained,then reduced the corrosion rate in the electrochemical corrosion. In high temperature and high pressure CO2corrosion, due to the different content of Cr-Al, the steel formed different morphology of corrosion product film. The corrosion product film of steel contenting lower Cr-Al was given priority to FeCO3crystals, while the higher Cr-Al content was given priority to amorphous form with Cr compounds and Al oxide. The corrosion of Cr-Al alloy steel has formed corrosion product layer enriched with Cr, Al, thus effectively slows down the corrosion.