【摘要】 采用无铵助镀工艺对基体进行预处理,分别在450℃的纯锌浴和Zn-0.05%Al合金浴中制备了镀层,借助SEM、EDS等分析对比了两种锌浴中镀层的形成和微观组织结构,探讨了无铵助镀条件下Zn-0.05%Al合金浴中Al对镀层形成过程及组织结构的影响。结果表明:无铵助镀条件下锌浴中添加0.05%Al可显著提高镀层的外观质量并使镀层厚度减薄;随着浸镀时间的延长,最终两种锌浴中制备的镀层均由ζ₁、ζ₂、δ和η相组成。0.05%Al的添加可以降低镀层中合金相层的厚度,在镀层形成的初始阶段抑制了ζ相的生成和长大,延迟了ζ相的分层;0³00 s浸镀时,两种锌浴中合金相层的生长速率主要受扩散速度控制,Zn-0.05%Al合金浴中浸镀时间≤30 s时,合金相层的生长速率受界面反应速度控制。更多还原

【Abstract】 The substrate was pretreated by ammonium-free fluxing,and zinc coating was galvanized by hot-dipping in pure zinc bath as well as Zn-0. 05%Al alloy bath at 450 ℃ respectively. Formation process and microstructure of the zinc coatings were analyzed by SEM and EDS,and effect of Al in Zn-0. 05%Al alloy bath on the formation of the coating with ammonium-free fluxing was discussed. The results show that the addition of 0. 05%Al in zinc bath could significantly improve the appearance quality and reduce the thickness of the coating. With dipping time increasing,the final coatings that is formed during hot dip galvanizing in pure zinc bath as well as Zn-0. 05%Al bath,consists of a series of Fe-Zn intermetallic layers,which have been identified as ζ₁,ζ₂,δ and η. The addition of 0. 05%Al in zinc bath can adequately reduce the alloy layer thickness,suppress the nucleation and growth of ζ phase in the initial stage of galvanizing,and postpone the layering of ζphase. When dipping time from 0 to 300 s in pure zinc bath as well as Zn-0. 05%Al bath,the alloy layer growth is mainly controlled by a mechanism of atomic diffusion rate. When dipping time in the Zn-0. 05%Al bath less than 30 s,the alloy layer growth is mainly controlled by a mechanism of interface reaction.更多还原