Electrochemical Experimental Study On The Low Temperature Dew Point Corrosion Of Atmospheric Tower Overhead System Parts

Dew point corrosion at low-temperature part of atmospheric equipment is a difficultproblem of the lifetime and safety of refinery equipments, the complex system structure andthe numerous corrosion influencing factors makes the system’s corrosion serious and difficultto control. When oil gas through low temperature spot equipment surface, and achieves timethe dew-point temperature, will form the strong corrosive acidic dew point. Domestic andforeign has carried on the massive material anticorrosion and the dew point corrosionenvironment research, but has not had the electrochemistry response characteristic researchwhich corrodes to the dew point.This article based on the analysis of the formation of dew point corrosion environmentalfactors, determining the dew point corrosion simulation environment as the main medium foranaerobic conditions in an acidic aqueous solution, the Hydrogen ion concentration was0.01mol/L, pH value was2and an ambient temperature of75℃and95℃, the temperaturedetection part of common steel (low alloy steel16MnR and austenite stainless steel0Cr18Ni9)dew point corrosion, electrochemical impedance and electrochemical noise responsecharacteristics, and determines the electrochemical noise used in refinery actual detection andthe feasibility of monitoring. In order to determine the dew point corrosion mechanism,formation conditions, electrochemical noise technique applied in refinery is actual, to lay thepreliminary foundation.Based on the center area and the edge area of dew point corrosion of power, selection ofdynamic simulating test of dew point corrosion center area, static simulation test of dew pointof marginal zone corrosion.Completed in a simulated environment, low alloy steel16MnR and austenitic stainlesssteel0Cr18Ni9electrochemical polarization experimental study.Analysis: the static,16MnR at75℃and95℃corrosion corrosion rate were7.0012mm/a and17.048mm/a; dynamic,16MnR at75℃and95℃corrosion corrosion rate were23.164mm/a and31.871mm/a.Static,0Cr18Ni9at75℃and95℃in the corrosive environments pitting potential were198.69mVand178.84mV; dynamic,0Cr18Ni9at75℃and95℃in the corrosive environments pittingpotential respectively150.71mV and138.27mV. Completed in a simulated environment, low alloy steel16MnR and0Cr18Ni9austeniticstainless steel by electrochemical impedance experimental study.Analysis: the static,16MnRat75℃and95℃in corrosion environment of impedance values were43.24.cm~2and15.32.cm~2; dynamic,16MnR at75℃and95℃corrosion environment of impedance values arerespectively11.42.cm~2and5.81.cm~2.Static,0Cr18Ni9at75℃and95℃in corrosionenvironment of impedance values were86.3.cm~2and65.69.cm~2; dynamic,0Cr18Ni9at75℃and95℃corrosion environment of impedance values are respectively60.9and43.2.cm~2Completed in a simulated environment,16MnR low alloy steel and austenitic stainlesssteel0Cr18Ni9experimental study of electrochemical noise.Analysis: the static,16MnR at75℃and95℃in corrosion environment noise resistance, pitting index, noise powerspectrum slope were9.8513×10~5,0.89461,-0.40and6.7848×10~5,0.86247,-0.58;dynamic,16MnR at75℃and95℃in corrosion environment noise resistance, pitting index,noise power spectrum slope were2.7568×10~4,0.83623,-0.97and1.1545×10~4,0.81239,-1.06.Static,0Cr18Ni9at75℃and95℃in corrosion environment noise resistance, pittingindex, noise power spectrum slope were4.9304×107,1.0608,-0.20and8.0073×10~6,1.0564,-0.27; dynamic,0Cr18Ni9at75℃and95℃corrosive environment, the noiseresistance the Kong Shi index, noise power spectrum slope were4.2299×10~6,1.0344,-0.29and1.1287×10~6,1.0202,-0.37.Based on the experimental results of electrochemical polarization, electrochemicalimpedance and electrochemical noise response characteristics of the study, gives a differentmethod of dew point corrosion characterization of situation.The environment simulation,electrochemical noise technique should be in the dew point corrosion detection, in order tosolve the low temperature dew point corrosion of atmospheric distillation unit overheadposition mechanism of electrochemical detection and monitoring, and provides the reference.