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The Investigation on Effect of Pickling and Activation on Electroplating and Electroless Plating on Magnesium Alloys

Author: ZhuYanPing
Tutor: YuGang
School: Hunan University
Course: Physical and chemical
Keywords: Magnesium alloy Pickling Activation Dip zinc Plating Electroless plating
CLC: TQ153.1
Type: Master's thesis
Year: 2009
Downloads: 292
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Abstract


Magnesium alloy has excellent overall performance, known as the \Magnesium chemical reactivity, poor corrosion resistance, limiting the development and application of magnesium alloy. Electroplating and electroless plating can significantly improve the corrosion resistance of magnesium alloy, wear resistance, solderability, conductivity and decorative, with good development and application prospects. Magnesium alloy is a difficult plated substrate, whether the implementation has a crucial role as well as the quality of the coating reasonable pre-treatment of electroplating and electroless plating. Pickling and activation is a key step in the pre-treatment, but traditional pickling and activation processes contain substances toxic to humans and the environment. This thesis environmental pickling and activation process before electroless nickel and electroless nickel AZ91D and AM60 magnesium alloy interface reaction and film formation mechanism in the pickling solution and activation solution discussed pickling and activation formulations and process conditions on AZ91D and AM60 magnesium alloy electroplating nickel and chemical plating nickel effect, to establish the most suitable for electroless nickel and chemical nickel plated pickling activation process. The results show that: 1. Pickling process and conditions of the corrosion rate of magnesium alloys, surface morphology and coating quality impact. The HNO 3 H 3 PO 4 and the HNO 3 CrO 3 pickling after magnesium The alloy surface is rough, the coating and the substrate of the obtained mechanical bite force preferably, corrosion resistance, respectively, is desirable before the pickling process in electroless nickel plating and electroless nickel. 2.HF activation energy in magnesium alloy surface to form a layer of dense fluoride membrane protective matrix: NH 4 HF 2 activated magnesium alloy surface to form a layer of denser fluoride film, but slightly lower activation than HF fluoride membrane dense; K 4 P 2 O 7 activation using the K 4 P 2 the complexation of the O 7 's, to remove surface oxides and hydroxides of magnesium alloy, magnesium alloy exposing fresh matrix and the formation of a new layer with microporous the hydroxide film; H 3 of the PO 4 KMnO step pickling activation, magnesium alloy formed on the surface layer of the oxide of manganese and phosphate mixed film to protect the substrate temporarily. The composition and properties of the activated film will directly affect the quality and performance of the coating. The 3.HF activation and NH , 4 the HF 2 activation activation film denser dip zinc layer uneven general corrosion resistance of electroless nickel layer; K 4 P 2 O 7 activation get more uniform thin film activation uniform dip zinc coating, electroplating nickel layer dip zinc corrosion resistance and cohesion are good; H 3 the PO 4 KMnO 4 step pickling activation of dip zinc-activated membrane fraction dissolved, dip zinc more fully, and good corrosion resistance obtained by the electroless nickel plating layer, but with the binding force of the base body to be improved. Magnesium alloy plating nickel before the best activation process K 4 P 2 O 7 activation, the best composition and process conditions: K 4 P 2 O 7 · 3H 2 O 120 ~ 200 g · dm -3 < / sup>, Na 2 CO 3 10 ~ 30g · dm -3 , KF · 2H 2 O 11g · dm -3 , 70 ± 5 ℃, 2 ~ 3 min. Electroless nickel plating before the best activation process for the two-step activation process, namely HNO 3 H 3 PO 4 pickling K < sub> 4 P 2 O 7 activation NH 4 HF 2 activation. Performance obtained by this process of electroless nickel deposits with via traditional HNO 3 the CrO 3 the pickling and HF activation plating performance is quite good corrosion resistance, adhesion avoid the the traditional craft toxic chromium compounds and high volatile hydrofluoric acid application.

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