高流速海水中金属材料的腐蚀行为

CORROSION BEHAVIOUR OF METALLIC MATERIALS IN HIGH VELOCITY SEAWATER

一、前言金属材料在自然海水中的腐蚀数据通常是在自然海流(0.1～1米/秒)条件下获得的,但滨海的电站、石油、化工系统中的高流速管道、泵、热交换器、阀门以及高速舰船中的管道以至船体等,都处在较高流速(5～30米/秒)海水的环境中。因此。

By using tubular test loop for corrosion in high velocity seawater, the potential and corrosion rate of some typical marine carbon steel, marine low alloy steels, 18-8 stainless steel, two copper alloys and one each aluminium alloy and titanium alloy have been measured at different flow rates of seawatrer. The corrosion rate at high velocity is several times higher than that in natural condition and has different characteristics. X-ray diffraction of the rust layer on steels indicates that majority of the rust layer is γ-FeOOH and no Fe_3O_4 is detected. The dependence on galvanic current from four couples on seawater velocity has been studied. The galvanic current in flowing seawater is several to dozens of times higher than that in static condition. When steels are coupled with a noble metal, the galvanic current does not change much with velocity of seawater. When Zn-Al-Cd is used as sacrificial anode to protect iron and steel, special attention should be paid to the effect of velocity.