本研究使用實施覆銲(IN-52M)之異質銲接件(A508/IN-182/316L-308L緩衝層)浸泡於靜滯鹽水環境並添加腐蝕抑制劑。透過電化學儀器分析合金在環境之腐蝕特性，以及配合浸泡試驗之表面觀察、腐蝕產物之成分分析與材料損失量，探討腐蝕機制及腐蝕損失與電化學相關性。
實驗結果顯示，在鹽水環境中，316L、308L、IN-182、IN-52M的鉻含量足以在金屬表面形成穩定的鈍化膜，以至於有相近的腐蝕電位及較低的腐蝕電流。A508在本異質銲接件系統中有最大的腐蝕電流密度及最低的腐蝕電位，與其它合金相差達 500 mV至600 mV，因此A508為陽極金屬。再者，A508熱影響區之微觀組織為每道熱影響組織依序彼此相連排列，其中耐蝕性較差之組織易成為局部陽極區，加上異質界面的成分急劇變化產生加凡尼腐蝕，使熱影響區產生規律之腐蝕形貌以及在兩銲珠之交界處有最大的腐蝕深度。在距離異質界面較遠的A508母材受加凡尼腐蝕影響不明顯，為均勻腐蝕。隨時間增長，A508表面的腐蝕產物沉積量增加，阻礙腐蝕環境與材料表面接觸，使其腐蝕速率逐漸減緩。A508添加鉬酸鈉比硝酸鈉抑制劑至6000 ppm : 4000 ppm 時有鈍化產生，腐蝕電位由 -916 mVSCE 提升至 -388 mVSCE，接近316L、308L、IN-182、IN-52M的腐蝕電位，減緩加凡尼腐蝕。腐蝕抑制劑添加不足時，A508表面出現不受異質界面加凡尼腐蝕影響，隨機分布的蝕孔。浸泡足夠的腐蝕抑制劑(鉬酸鈉:硝酸鈉 = 6000 ppm : 4000 ppm)，在A508表面生成薄且具保護性之氧化鐵及局部的鐵與鉬酸根之錯合物，具有抑制效果。

In this study, dissimilar weldments(A508/IN-182/316L-308L buttering) that were carried out overlay welding(IN-52M) were immersed in with or without inhibitors additional of salt water environment. The corrosion characteristics of the alloy were analyzed by electrochemical instruments. The immersion test was adopted to investigate the corroded appearance, the composition of the corrosion products and the corrosion depth. Meanwhile, the corrosion mechanism and the correlation between corrosion loss and electrochemistry were discussed.
In the experimental results, the chromium and nickel content of 316L, 308L, IN-182, and IN-52M were sufficient to form a stable passivation film on the metal surface. As a result, it had similar corrosion potential and lower corrosion current in the salt water environment. A508 had the lowest corrosion potential in this dissimilar weldment system, the potential different was 500 mV to 600 mV lower than other alloys. Furthermore, A508 has a larger corrosion current density. Therefore. A508 was an anode metal. The appearance of the A508 heat-affected zone was composed of heat-affected microstructures connected and arranged in sequence. Among them, the portions with poor corrosion resistance was easy to become a local anode zone. And the instantaneous change in composition of the dissimilar interface produced galvanic corrosion. It caused heat-affected zone had a regular corrosion morphology and the maximum corrosion depth at the junction of the 2 weld beads. However, the A508 base metal that was far away from A508/IN-182 interface was not significantly affected by galvanic corrosion. As the development of corrosion behavior, corrosion products were kept producing, and deposited on the surface of A508, which hindered the contact between the environment and the surface of the material. As a result, its corrosion rate was gradually slowed down. The passivation was observed at the ratio of Na2MoO4 and NaNo2 inhibitors was 6000 ppm : 4000 ppm. Furthermore, the corrosion potential of A508 was increased to -388 mVSCE, and it was closed to the corrosion potential of 316L, 308L, IN-182, and IN-52M, which slowed down the galvanic corrosion. In contrast, the insufficient addition of corrosion inhibitors caused pitting corrosion on the surface of A508, and it was not affected by galvanic corrosion at the dissimilar interface. Sufficient corrosion inhibitors(Na2MoO4 : NaNo2 = 6000 ppm : 4000 ppm) would formed thin and protective Fe2O3 and local complex of iron and molybdate were observed on the immersed surface.

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