Effect of Borax Pentahydrate Addition to Acid Bath on the Microstructure and Corrosion Resistance of Zn-Co Coating

Abstract

In this work, the Zn-Co coatings were synthesized on AISI 4140 steel and aluminum plates by using potentiostatic electrodeposition technique in sulphate-based acidic baths with 0, 20, 40 and 60 g l −1 of borax pentahydrate, as additive. The effect of borax pentahydrate on the microstructure of the samples was observed using scanning electron microscopy and X-ray diffractometer. The deposition process was investigated by cyclic voltammetry. The effect of borax pentahydrate on the corrosion resistance of the samples was studied by potentiodynamic polarization technique. The results have demonstrated, that the addition of borax pentahydrate was in favor of the growth of grains. The morphology of pyramidal islands on the surface was changed to a more flat structure. The results have also demonstrated that the effect of borax pentahydrate was not monotonous. With increasing concentration, the corrosion potential was at minimum and the charge transfer resistance Rt was at maximum for the sample obtained from the bath with 60 g l −1 of borax pentahydate, indicating that this sample showed the best corrosion resistance. It was found that current density first decreased and than increased, due to adsorption of a complex of borax pentahydrate and/or changes in the morphology, however, the initial deposition potential was not affected. The addition of borax pentahydrate to the bath led to formation of the best Zn-Co deposits, composed of coalesced globular fine grains, smaller than ≈2 µm in diameter. In addition, all of the studied Zn-Co deposits consisted of η phases. It is suggested that Zn-Co deposits produced in the bath containing 60 g l −1 of borax pentahydrate probably offer sacrificial protection to the steel substrate.

Effect of the Applied Current Density on the Structural and Magnetic Properties of the Electrodeposited Cobalt-Nickel Alloy Thin Films

“…It is reported that anomalous codeposition can be either enhanced or suppressed by controlling experimental parameters of electrochemical depositions [23]. For codeposition of Co and Ni alloys, deposition of Co is mainly controlled by diffusion.…”

Characterization of Alumina-Titania Coatings Produced by Atmospheric Plasma Spraying on 304 SS Steel

“…Too short spraying distance will produce lower adherence due to overheating and resulting internal stress inside the coating. In contrast, too long spraying distance will decrease the adherence bonding due to cooling and deceleration of the particles flying in the plasma beam [16]. …”

Pulse Electrodeposition of Copper-Zinc Coatings from an Alkaline Bath

“…Cu-Zn alloys have attracted attention due to their corrosion resistance and decorative applications [1][2][3][4][5]. CuZn electrodepositions were produced by using cyanide and non-cyanide baths, namely from electrolytic solutions based on complexing agents such as gluconate, citrate, EDTA, tartrate, sorbitol, glucoheptonate, pyrophosphate or mannitol [6][7][8][9][10].…”