The effect of substrate on the electroless nickel plating of Mg and Mg alloys
The effect of substrate on the electroless nickel plating of Mg and Mg alloys
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DOI：
10.1016/j.surfcoat.2004.12.001
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发表时间：
2006-03
影响因子：
5.4
通讯作者：
Zhenmin Liu;Wei Gao
中科院分区：
文献类型：
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作者：
Zhenmin Liu;Wei Gao
镁（Mg）及其合金由于其高的强度重量比和相对高的刚度而被用作工业中的结构部件。镁基合金的缺点是其高电化学活性和差的耐腐蚀性。因此，需要进行涂层或表面处理以达到保护目的。本文报道了我们在镁合金上化学镀镍的研究工作。以纯镁、AZ31和AZ91镁合金为基体，研究了化学镀镍层的沉积速率、形核过程、化学成分和微观结构。结果发现，沉积过程的强烈影响的合金基板。在AZ31镁合金上电镀镍具有较高的沉积速率和较低的表面粗糙度。扫描电镜观察表明，镍镀层在基体上形成了球状形貌。镀前化学预处理显著增加了基体表面粗糙度。在电镀过程的早期阶段，基体的微观结构强烈影响。由于晶粒间的电偶耦合，沉积开始于相和晶界上。AZ31合金等细小的基体组织为化学镀镍提供了大量的形核位置，有利于化学镀镍的形核和生长过程。AZ31和AZ91镁合金表面涂层的结合强度均高于纯镁表面。AZ31的临界载荷（粘合强度的量度）达到13.1N。
Magnesium (Mg) and its alloys are being used as structural components in industry because of their high strength-to-weight ratio and relatively high stiffness. A shortcoming of Mg based alloys is their high electrochemical activity and poor corrosion resistance. Therefore, coatings or surface treatment are needed for protection purpose. This paper reports our work on electroless plating of Ni on Mg alloys. Pure Mg, AZ31 and AZ91 Mg alloys were used as the substrates to investigate the deposition rate, nucleation process, chemical composition and microstructure of the electroless Ni coatings. It was found that the deposition processes are strongly affected by the alloy substrates. Ni plating on AZ31 alloy has higher deposition rates and lower surface roughness than that of other substrates. SEM investigations showed that nodular morphology of Ni coatings formed on the substrates. Chemical pre-treatment before plating increases the substrate surface roughness significantly. The plating process was strongly influenced by the substrate microstructure at the early stage. Deposition was initiated on the phase and grain boundaries due to the inter-grain galvanic coupling. Fine substrate microstructure such as that of AZ31 alloy provided a large amount of nucleation sites, benefiting the nucleation and growth processes of the electroless nickel plating. The adhesion strengths of the coatings on AZ31 and AZ91 alloys are higher than that on pure Mg. The critical load (a measure of adhesion strength) of AZ31 reached 13.1 N.