| Galvanic corrosion exists common in the industry of oil and gas, which would cause the pipelines and heat exchangers corrosion failure frequently, and make enormous economic losses and serious environment pollution because the exist of acidic gas, for example carbon dioxide and acetic acid. The effects of materials’ characteristic, cathode/anode areas ratios and environmental factors on galvanic corrosion in CO2-saturated solution in the presence of HAc were studied in order to provide a realiable reference for industry on reasonable selection of materials.Corrosion potentials of ten kinds of materials including seven structural materials, three sacrificial anodes in CO2-saturated with3%NaCl solution in the presence of acetic acid were measured by using electrochemical test methods and got a galvanic series:316L> copper>Ti>brass>2Crl3>N80>A3>Zn>Al>Mg. At the same time,316L,2Cr13, N80, A3steels were selected as researched electrodes that made up29kinds of couples with others materials in all. The effects of materials’characteristic, cathode/anode areas ratios on the couples were studied. The results showed that galvanic corrosion rate depended on the potential difference and polarization characteristic.316L,2Crl3steels were effective cathode materials, the galvanic effects of titanium, copper, brass were less than that of316L,2Cr13. All of couples except316L/Ti were controlled by cathode process, the couple of316L/Ti was controlled by anodic process. The couples of316L/copper,316L/brass occurred polarity reversal when the couple were jointed, but the polarity would get right after several minutes. The galvanic current density between Ti and the working electrodes was very small, that was less2-3times than the couples of copper, brass with working electrodes. Sacrificial anodes of Zn, Al and Mg had a significant protective effect on the structural materials. However, the self-corrosion rate of Mg was poor compared with Zn, Al. Galvanic current density and galvanic effect increased with the increased Sc/Sa. At the same time, galvanic effect changed according to the rules.The effect of cathode/anode area ratios and environmental factors including temperature, Cl-and HAc on galvanic corrosion behavior of the couple of2Crl3/N80were studied by using electrochemical test method, scanning electronmicroscopy (SEM), X-ray diffraction (XRD). The results showed that:the galvanic current density of2Crl3/N80increased along with the increase of cathode/anode area ratio. Cathode/anode area ratio was less than1:1, the galvanic effect by increased cathode area of the couple was higher than that effect of cathode/anode area ratio was greater than1which cathode area increased. Galvanic corrosion of2Cr13/N80would become more serious with the temperature increased, for instance, the corrosion rate of80℃was about8.29times more than the corrosion rate of30℃. The galvanic current density of2Cr13/N80reached biggest value at the concentrate of500ppm HAc. Beyond this concentrate of HAc, the corrosion density was less than that the current density with the solution in absence of HAc. The galvanic current density of2Cr13/N80had a minimum value at the concentrate of30g/LNaCl, and a maximum value at the concentrates of10%NaCl. The concentrate of Cl-increased, then the pitting corrosion of N80steel was promoted. The galvanic effect of2Cr13/N80changed according to the law in environment factors. |
PDF Full Text Request