沃斯田鐵系不銹鋼進行週期性噴灑氯化鎂水溶液的腐蝕行為探討

The corrosion behavior of austenitic stainless steels under periodic spraying magnesium chloride solution

本實驗的研究對象為乾貯用沃斯田鐵系不銹鋼，藉由週期性噴灑氯鹽溶液，於不同的溫度條件下進行加速腐蝕實驗，探討沃斯田鐵系不銹鋼在沿海環境中，對氯離子誘發應力腐蝕龜裂的敏感性。
本實驗使用固溶及敏化熱處理之304、304L、316L不銹鋼U-bend試片，週期性噴灑氯化鎂水溶液，在40、60、80℃及固定相對濕度40%的結果中，可以發現304、304L不銹鋼在40、60℃下，表面有觀察到裂縫生成，在80℃下以大面積的孔蝕聚合為主要腐蝕型態；316L不銹鋼在40、60℃下裂縫生成數量較少，以孔蝕為主，在80℃下則出現較長的裂縫。根據橫截面的觀察結果，往縱深方向擴展的裂縫具有分支特性，為應力腐蝕裂縫，在本實驗中，以敏化316L不銹鋼在80℃下觀察到的裂縫，具有較大的深度。

The research object of this experiment is austenitic iron stainless steels for dry storage system. By periodically spraying chloride solution, accelerated corrosion experiments were conducted under different temperature conditions to investigate the susceptibility of austenitic iron stainless steel to chloride-induced stress corrosion cracking nearby coastal environments. Solution-annealed and sensitization heat-treatments U-bend specimens were applied in this corrosion-accelerated experiment with periodic spraying magnesium chloride solution, and test conditions were set at 40, 60, 80℃ with constant relative humidity 40%RH. The test results of 304 and 304L stainless steels indicated an obvious trend was that stress corrosion cracking was almost observed at 40, 60℃and general corrosion was dominant corrosion type at 80℃. For 316L stainless steel, pitting corrosion was dominant corrosion type at 40, 60℃, and stress corrosion cracking was relatively at 80℃. According to the cross-section observation, the cracks observed on 316L stainless steel displayed highly-branched, which indicated the cracks were stress corrosion cracking. In this experiment, the cracks observed on sensitized 316L stainless steel at 80℃ showed a largest depth.