25钢在热带海洋环境下海水中的微生物腐蚀及其对力学性能的影响

通过对比25钢在热带海洋环境下自然海水和无菌海水中的平均腐蚀深度，研究微生物对碳钢腐蚀行为的影响。结果表明，海水中微生物的存在显著影响碳钢的平均腐蚀深度。浸泡时间为365 d时，在自然海水中的腐蚀深度为无菌海水中的2.6倍，产生了明显的局部腐蚀。无菌海水和自然海水腐蚀都会造成材料抗拉强度的下降，对比发现腐蚀时间较长时自然海水中材料抗拉强度下降更大，说明微生物腐蚀对材料抗拉强度有一定影响。微生物腐蚀对材料抗拉强度的影响作用，主要在于微生物的存在使材料的平均腐蚀深度增大，引起材料横截面积的减小。微生物腐蚀并不会降低退火25钢的延伸率和夏比冲击功，实验过程中未发现微生物作用下材料的氢脆现象。

EFFECT OF MICROBE ON THE CORROSION BEHAVIORS AND MECHANICAL PROPERTIES OF 25 CARBON STEEL IN TROPICAL SEAWATER CONDITION

In this work, the single effect of microbe on the corrosion behaviors of 25 carbon steel is studied by comparing the average corrosion depth of the carbon steel in natural seawater and in sterile seawater in tropic condition. Through examining the strength and Charpy impact absorbed energy after different corrosion periods, the effects of microbiologically influenced corrosion (MIC) process on mechanical properties of 25 steel are illustrated. The results show that the bacterial activity at the interface accelerates the corrosion of 25 steel. When the corrosion time is 365 d, the average corrosion depth of 25 steel in natural seawater is 2.6 times higher than that in sterile seawater. Localized attack is also observed on the specimens immersed in natural seawater for 365 d. The corrosion of 25 steel in natural seawater and sterile seawater reduces the ultimate tensile strength of 25 steel, and this effect is more notable during the corrosion in natural seawater than in the sterile seawater. The analysis reveals that the decrease of the ultimate tensile strength is related to the increase of average corrosion depth. MIC does not decrease the elongation and Charpy impact absorbed energy of the annealed 25 steel, and MIC induced hydrogen embrittlement is not found.