高温高酸性环境下镍基合金718与异种金属偶接的电偶腐蚀行为

高温/高压高酸性腐蚀环境中镍基合金718常作为可靠的材料使用,但不可避免会与其他金属偶接使用,易产生电偶腐蚀。模拟150℃,H_2S分压1.0 MPa,CO2分压1.5 MPa,Cl~-浓度200 000 mg/L的高温高酸性腐蚀环境,采用高温高压电化学测试技术和浸泡腐蚀模拟试验,研究了镍基合金718分别与低合金钢35Cr Mo、C110和不锈钢13Cr偶接后的电偶腐蚀行为。结果表明:在模拟高温高酸性环境下,3种金属分别与718合金偶接后,均发生了一定程度的电偶腐蚀,其中C110电偶腐蚀速率最大,而不锈钢13Cr的电偶腐蚀速率最小。电偶腐蚀的驱动力是2种金属的自腐蚀电位差,异种金属偶接后的电偶效应与两偶接材料的电位差成正比,而阳极材料自身的极化特性决定了其与耐蚀合金偶接后的电偶腐蚀程度。

Galvanic Corrosion Behavior of 718 Nickel-Based Alloy Coupled with Dissimilar Metal in High-Temperature and High-Acidic Environments

Nickel-based alloy 718 was a kind of reliable material in high-temperature and high-acidic environment,however,it was used inevitably with dissimilar metal which would appear severe galvanic corrosion.A high-temperature and high-sour environment of 150 ℃,1.0 MPa H2S partial pressure,1.5 MPa CO2 partial pressure and 200 000 mg/L Cl-was simulated,and the electrochemical tests in a high-temperature and high-pressure autoclave and immersion corrosion tests were conducted to investigate the galvanic corrosion behavior between nickel-based alloy 718 and 35CrMo steel,C110 steel or 13Cr stainless steel,respectively.Result showed that under the simulated high-temperature and high-acidic environment,the three kinds of alloy respectively coupled with alloy 718 had undergone some degree of galvanic corrosion.Among the three couple,the galvanic corrosion rate of C110 was maximum,and the rate of stainless steel 13Cr was minimal.The driving force of galvanic corrosion was the corrosion potential difference between two dissimilar metals,and the galvanic couple effect of dissimilar metals was proportional to the potential difference of two couple-materials.Besides,the polarization characteristics of the anode material determined the galvanic corrosion extent after coupled with corrosion-resistant alloy.