Thermodynamic, Adsorption Isotherms and Electrochemical Investigations of Nickel Electroplating on Mild Steel in Electrolyte Containing Deoxyribonucleic Acid from Citrus aurantium as Additive.

Different concentrations of Citrus aurantium with deoxyribonucleic acid as additive (Citrus aurantium_DNA) were co-deposited with nickel via electrodeposition. The coatings were formed in an aqueous nickel bath with the incorporation of Citrus aurantium_DNA concentrations at different temperatures, and the influence of the acid and the temperature on the microstructure of the coatings was studied. The data via adsorption isotherms were also analyzed. The characteristics of the morphological structure of the coatings were examined by scanning electron microscopy. The results demonstrated that Citrus aurantium_DNA additives were evenly dispersed on the mild steel surface during the nickel coatings deposition; a current density of 1.5 A/dm³ used during the electrolysis process was favourable in attaining the maximum coating efficiency (~70%) at 25°C and 20 mg/L of Citrus aurantium_DNA. The optimum temperature for electroplating was found to be 25°C. The data spawned from the adsorption Freundlich and Langmuir isotherms showed two preferred temperatures: i.e. 25 and 40°C via the former and 55 and 70°C via the latter. The thermodynamic assessment confirms that the adsorption mechanism of the Citrus aurantium_DNA additive in a Ni electrolyte solution on mild steel in an HCl solution is physisorption at the investigated temperatures. X-ray diffraction revealed some broad peaks signifying an amorphous structure at all Citrus aurantium_DNA concentrations. [ABSTRACT FROM AUTHOR]