Surface characterization of zincated aluminium and selected alloys at the early stage of the autocatalytic electroless nickel immersion process

Abstract

In this work the changing structure of nickelphosphorus deposits on aluminium and its alloys at the early stage of electroless nickel phosphorus deposition using hypophosphite ion as reducing agent has been studied. Prior to electroless nickel deposition, zincating is used for pre-treatment of aluminium substrates. The surface morphology and structure of the electroless Ni-P layers were characterized by scanning electron microscopy and X-ray diffraction analysis. Results show that Ni-P deposition is closely related to the dissolution of the zincating layer, followed by progressive nickel nucleation. The nuclei serve as a catalytic surface for further Ni-P deposition which increases with deposition time. The growth and coalescence of the nuclei on the aluminium substrate results in crystalline layers of Ni-P.

Long-term stability of Cu/Pd nanoparticles and their feasibility for electroless copper deposition

“…Similar porous structures of copper deposits were observed for these three nanoparticles systems at this stage, which mainly reflecting the nature of porous FR-4 substrate. The porous structure would be gradually filled after long deposition time with suitable activator and bath condition, which has also been reported in the case of electroless Ni plating on various of substrate [28,29].…”

Zincating Effect on Corrosion Resistance of Electroless Ni‐P Coating on Aluminum Alloy 6061

“…Such oxide film prevents aluminum substrates to be plated with good adhesion. The most satisfactory and practical method available for aluminum preparation prior to further deposition is zincating . Zincating is an electrochemical exchange reaction between zinc complexes in the solution and the aluminum substrate, depositing zinc crystallites at the expense of aluminum dissolution.…”

“…In order to achieve a better adhesion strength of the Zn layer, a multiple immersion zincating operation is recommended , . However, the most common practice is the double zincating process , , , .…”

“…The corrosion behavior of electroless Ni‐P coatings is controlled by three main parameters: (i) to what extent the coating is amorphous, (ii) the percentage of phosphorous content, and (iii) the degree of internal stress. It is generally observed that electroless Ni‐P coatings are more corrosion resistant when they are amorphous , , . Such behavior has been attributed to the features of the amorphous state, a homogeneous structure and absence of grain boundaries, dislocations, kink sites and other surface defects , .…”

Comparison of anodic dissolution, surface brightness and surface roughness of nanocrystalline nickel coatings with conventional decorative chromium coatings

“…Ni-P coatings obtained by electroless deposition of nickel from solutions containing hypophosphate ions also have desirable properties such as high hardness, good wear resistance and corrosion resistance [6,7]. However, electroless nickel deposition technique can be an expensive option due to the cost of reducing agents.…”