本研究探討電弧銲接後銲件各部份的微觀金 相變化與腐蝕情形，以暸解國内水下工程業界常 用之銲條，在海水環境所銲接的銲件與大氣銲件 之腐蝕性質差異。所採用的母材為造船工業常用 之低碳結構鋼材JIS SS 41，銲绦則為絕緣膠套包 覆之銲條CNS E4301 o
一般而言，水下銲件之微觀金相組織晶粒粒度較大氣中銲件為粗大3兩種環境銲件之銲道與 熱影響區，其腐蝕電位或開路電位，呈顯相反趨 勢：即大氣銲件之熱影響區較易腐蝕，而水下銲 件卻是銲道較易腐蚀：此結果與浸潰腐蝕之現象吻合°

This study is focused on the effect of microstructure on the corrosion behavior of marine-used structural steel weldments produced by conventional welding and underwater welding
respectively. The SMAW is applied for both under seawater welding and atmospheric welding. CNS E4301 wrapped with plastic for water proof is used as a welding electrode to join JIS SS 41 structural steel.
Underwater weldments show a coarser grain size than the weldments made in atmosphere. The corrosion properties exhibit the weld metal of underwater weldments prefers to corrode, but the heat affected zone of atmospheric weldments are the most active to corrode. The results of immersion、tests of the weldments are consistent with the measurement of dynamic polarization curves .