碳鋼、耐候鋼與鍍鋅鋼在不同腐蝕環境近十年之大氣腐蝕行為研究

A Study of almost 10 year Atmospheric Corrosion of Carbon, Weathering and Galvanized Steels in Various Environments

本研究是探討碳鋼、耐候鋼與熱浸鍍鋅碳鋼在不同腐蝕環境近十年之大氣腐蝕行為。研究方法是實際曝露試驗，以SEM/EDS與XRD進行腐蝕生成物分析。結果顯示不論在工業區、濱海區或鄉村區，腐蝕量是碳鋼＞耐候鋼＞鍍鋅鋼。裸露鋼材的腐蝕速率滿足C = AtB之定律（C與t分別表腐蝕量與時間，A、B為常數），且耐候鋼不僅在未生成銹層以前反應性比碳鋼低，而且在生成銹層後，其保護也較佳。腐蝕生成物組成，耐候鋼有較易產生α-FeOOH之傾向，而碳鋼有較易產生Fe3O4之傾向，鍍鋅鋼在工業區與濱海區的銹皮組成相當複雜，在鄉村區的銹皮組成祗有ZnO。鍍鋅鋼在工業區與濱海區的η相與ζ相都有受到腐蝕，在鄉村區祇有η相有受到腐蝕。結合前置研究結果，裸露鋼材在不同環境的腐蝕量是濱海區＞工業區＞多風都市區＞鄉村區。

This study is to investigate the atmospheric corrosion behaviors of carbon steel, weathering steel, and hot-dip galvanized carbon steel in various environments for almost 10 years. The experimental methods included actual exposure tests and analyses of corrosion products by SEM/EDS and XRD. The results revealed that, in industrial, coastal, and rural areas, the weight loss was ranked in the order: carbon steel weathering steel galvanized steel. The corrosion rates of bare steels obeyed the law C = AtB (C and t represent corrosion amount and time, respectively, while A and B are constants). The weathering steel not only possessed lower initial reaction rate, but also exhibited better protective rust than carbon steel. The corrosion product of weathering steel had more tendency of generating α-FeOOH, while that of carbon steel had more tendency of forming Fe3O4. The corrosion product of galvanized steel in both industrial and coastal areas were complex, while that in rural area was simply ZnO. Furthermore, both η and ζ phases were corroded in the above former two areas, while only η phase was corroded in rural area. Compared with that in previous study, the weight loss of bare steel in various areas was ranked in the order coastal >industrial >windy urban >rural.