热镀55%铝-锌钢板在青岛不同海水区带的腐蚀行为

开展了热镀55%铝-锌钢板在青岛不同海水区带的实海腐蚀测试,并利用电化学测试、失重腐蚀测试和扫描电镜首次研究了镀层的海水腐蚀行为.结果表明,由于腐蚀电流密度小,腐蚀产物具有保护性,55%铝-锌镀层在全浸区的耐蚀性能比镀锌层和5%铝-锌镀层好;由于保护性锌的腐蚀产物被滞留在富铝的枝晶网络中,充分的充气条件又促进了镀层富铝相的钝化,镀层腐蚀的传质过程受到明显抑制,所以55%铝-锌镀层在潮差区和飞溅区的耐蚀性能显著优于全浸区,是全浸区的2到3倍;值得注意的是,镀层在全浸区出现较严重的局部腐蚀.

Corrosion Behavior of Hot-Dip 55%Al-Zn Alloy Coated Sheet Steel Exposed to Different Seawater Zones in Qingdao

Commercial hot-dip 55 % Al-Zn alloy coated sheet steel was investigated for its seawater corrosion behavior in Qingdao through electrochemical measurements, weight loss tests and SEM, where the coating was exposed to different seawater zones. The results indicated that the 55 % Al- Zn coating is superior to conventionally galvanized coating and 5 % Al-Zn coating in anticorrosivity when its specimens were immersed in seawater because of its low corrosion current density and protective corrosion products. Since the protective zinc corrosion products are mechanically retained in the Al-rich interdendritic network to retard further corrosive attack and the wellaerated condition promotes the passivity of the Al-rich phase so as to inhibit greatly the mass transfer process of corrosion, the 55% Al-Zn coating shows better anticorrosivity in tidal and splash zones than in immersion zone, i.e., 2- 3 times as high as in immersion zone. What is worthy to notice is that serious pitting corrosion was found when the 55 96 Al-Zn coating specimens were in immersion zone.