Influence of activation on performance of nickel–phosphorous coating. (September 2015)

• Record Type: Journal Article
• Authors: Pan, Y.; Yu, G.; Hu, B.; Xie, Z.; Tran, T.; Zhang, X.
• Is Part Of: Surface engineering. Volume 31:Number 9(2015)
• Page Start: 685
• Page End: 692
• Publication Date: 2015-09
• Subjects: Surfaces (Technology) -- Periodicals; Coatings -- Periodicals; 620.4405
• DOI: 10.1179/1743294415Y.0000000052
• Languages: German
• ISSNs: 0267-0844

Abstract

<abstract> <title> <x content-type="archive" xml:space="preserve">Abstract</x> </title> <p>In order to optimise the activation process, the effect of three activation processes on the direct electroless nickel–phosphorous plating on AZ91D was studied. The properties of the activation coating and Ni–P coating were characterised with electrochemical tests, SEM and EDX. The results showed that an optimum activation coating for nickel deposition was developed via twice activations of K₄P₂O₇ and NH₄HF₂ respectively. The first activation in the K₄P₂O₇ solution could clean the surface and remove Mg₃(PO₄)₂ dust produced by pickling. The coating with proper 1·12–1·49 <italic>F</italic>/<italic>O</italic> ratio (at-%) composed of MgF₂ and MgO or Mg(OH)₂ was produced via second activation in NH₄HF₂ solution. Excess hydrogen produced by Mg with H⁺ in the plating bath could lead to high porosity and low adhesion of Ni–P coating. A compact Ni–P coating with better adhesion and corrosion resistance was explored in this research.</p> </abstract>