扩散处理对23MnCrNiMo54热浸镀铝钢耐蚀性的影响

Effect of thermal diffusion treatment on corrosion behavior of hot dip aluminized 23MnCrNiMo54 steel

对23MnCrNiMo54热浸镀铝热扩散前后的涂层结构、电化学性能和中性盐雾腐蚀进行分析。结果表明,扩散前表面涂层呈致密的铝-铁铝层结构,扩散后表面涂层转化为带裂纹和孔洞的铁铝层。扩散前后的表层自腐蚀电流低于23MnCrNiMo54钢自腐蚀电流两个量级,扩散后自腐蚀电位最高,表层材料耐腐蚀性增加。盐雾试验发现,23MnCrNiMo54钢抗腐蚀性较差,1 h出现锈点,热浸镀铝后显著提升抗腐蚀性,24 h尚未出现明显锈点,热浸镀铝涂层对23MnCrNiMo54钢的耐腐蚀性有明显改善。热浸镀铝再经扩散处理后,4 h出现锈点,扩散前后23MnCrNiMo54钢在中性盐雾中的耐腐蚀性差异较大。造成这种差异的原因主要是扩散后涂层上的缺陷和涂层较基体更低的电位。

Structure,electrochemical performance and corrosion resistance of hot dip aluminized 23MnCrNiMo54 steel before and after thermal diffusion were studied. The results show that hot dip aluminized 23MnCrNiMo54 steel has two dense layers of aluminum and ferroaluminum separately. Diffused hot dip aluminized 23MnCrNiMo54 steel has two layers,with disappeared aluminum layer and an additional layer of iron and aluminum infiltration. Pores and cracks can be observed in ferro-aluminum layer. The corrosion current of hot dip aluminized 23MnCrNiMo54 steel and diffused hot dip aluminized 23MnCrNiMo54 steel are two order magnitude smaller than 23MnCrNiMo54 steel. The corrosion potential of hot dip aluminized 23MnCrNiMo54 steel is the highest in three different treatments. Hot dip aluminized23MnCrNiMo54 steel has a great corrosion resistance ability. In neutral salt spray test( NSS test) the 23MnCrNiMo54 steel corrodes in 1 h,hot dip aluminized 23MnCrNiMo54 steel has no corrosion pits in 24 h,the corrosion resistance is enhanced significantly. Diffused hot dip aluminized 23MnCrNiMo54 steel starts to corrode after 4 h. The corrosion resistance of hot dip aluminized 23MnCrNiMo54 steel before and after thermal diffusion is distinctly different. The difference is mainly because of the pores and cracks in ferro-aluminum layer of diffused hot dip aluminized 23MnCrNiMo54 steel and the lower corrosion potential of diffused hot dip aluminized 23MnCrNiMo54 steel comparing to23MnCrNiMo54 steel.