碳鋼和耐候鋼4～8年大氣曝露腐蝕行為研究

A Study of Atmospheric Corrosion Behaviour of Carbon Steels and Weathering Steels Exposed for 4-8 Years

耐候鋼可分為三類來使用，(1)裸露，(2)銹安定化處理，(3)塗漆。為了瞭解在這三種狀況下，耐候鋼和碳鋼抗大氣腐蝕行為的差異以及找尋較適宜之銹安定化處理劑和塗裝系統，因此本研究乃將耐候鋼和碳鋼以此三種狀況下於台灣三個不同環境地區進行長期大氣曝露試驗。結果顯示耐候鋼之抗蝕性遠優於碳鋼，尤其是高磷含量者或於臨海工業地區，主要原因為耐候鋼會生成以非晶質鐵氧氫氧化物之內層銹層。在銹安定化處理劑以脲脂＋醇酸樹脂類之BAS-60 和新離子塗料最能適用於耐候鋼上，而磷酸鹽皮膜除於氯離子含量較高之臨海地區外亦能適用。塗裝上以使用無機鋅底漆＋環氧樹脂中塗漆＋聚氨基甲醇酯面漆效果較佳；同時於使用同一油漆系統下，耐候鋼之抗生銹性亦較碳鋼者為佳。

Weathering steels can be used by (1) bare base (2) rust stabilization and (3) painting. In order to understand the difference in atmospheric corrosion behavionurs of weathering and carbon steels in these three conditions and to find more suitable rust stabilization treatment and painting system, in this study, long term exposure test of weathering and carbon steels under these three conditions in three different emvironments in Taiwan has been performed. The results show that atmospheric corrosion resistance of weathering steel is superior to that of carbon steel, especially in steel containing high phosphorus or in coastal-industrial site, due to the formation of protective inner rust layer mainly being amorphous ferric oxyhydroxide on weathering steel. Urethane modified alkyd undercoat (BAS—60) and new ion - exchange coat can be used as rust stabilizers for weathering steels, while the phosphated treatment film also can be used except in the coastal environment. In painting, the paint system of inoganic zinc rich primer +epoxy based M.I.O. paint + polyurethane finish has better performance and the resistance of rusting of weathering steel is better than that of carbon steel after painting in the same paint system.