Effect of Zincate Treatment on Adhesion of Electroless Ni-P Coating onto Various Aluminum Alloys

Abstract

It is well known that the adhesion of the electroless Ni-P coating on aluminum alloy substrate can be remarkably improved by introducing the double zincate treatment as a pretreatment process. This study investigated the effects of the alloying element and zincate treatment on adhesion of electroless Ni-P coating on various aluminum alloy substrates using peeling test, FE-SEM and XPS. Surface morphology of zinc deposit from the 1st zincate treatment and its adhesive strength were changed, depending on the alloying element. The zinc deposit from the 2nd zincate treatment became uniformly thin, and the adhesive strength was improved irrespective of the alloying element. By dipping the zinc deposit obtained at the 1st zincate in 5% HNO 3 solution, most of the zinc deposit on aluminum substrate was dissolved, but XPS analysis revealed that the existence of zinc, whose state was metal, at the surface of aluminum alloy substrate after this dipping. This zinc at the surface should be an important factor influencing morphology of zinc deposit at the 2nd zincate treatment, so that zinc deposit became highly uniform and thin. This zinc at the surface can be attributed to the diffusion of zinc and aluminum between the zinc deposit from the 1st zincate and the aluminum alloy substrate.

Effect of heat treatment on surface characteristics and corrosion behavior of nickel plated AA2024 aluminum alloy

“…Over the years, many surface engineering techniques, including anodizing, electroplating, physical vapor deposition, surface melting and alloying, thermal spray coatings, plasma nitriding, ion implantation, and shot pinning have been investigated and used to enhance wear and corrosion resistance of aluminum alloys [5][6][7][8][9][10][11][12][13][14]. Economic efficiency, availability, high production speed, and no need for special industrial equipment are the positive aspects of the electroplating method, which in this study is used to create pure nickel coating on AA2024 alloy [15,16].…”

Nickel fluoride as a surface activation agent for electroless nickel coating of anodized AA1050 aluminum alloy

“…However, coatings without pre-treatments do often not give satisfactory results [7] due to rapid oxidation of the alloy surface, leading to the formation of a thin surface-oxide film, which reduces adhesive forces between the metal and the coating [7,8]. Therefore, electroless Ni-P coating of aluminum alloys, generally, requires pre-treatments using activators prior to the coating process [1][2][3][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Pre-treatments are classified into two categories: (i) single and (ii) double pre-treatments.…”

Electrodeposition of nickel from DES on aluminium for corrosion protection

“…In between the methods used is possible to cite the most widely used in the industry, the zincate process. [1][2][3][4] Ionic liquids (ILs) are the substitutes that can overcome the water solution limitations as reported in the literature. [5][6][7][8] Among their properties, besides the required chemical inactivity with aluminium, the most important are the good conductivity, the wide electrochemical potential window and the low vapour pressure.…”

“…In between the methods used is possible to cite the most widely used in the industry, the zincate process. 1-4…”