New non-cyanide acidic copper electroplating bath based on glutamate complexing agent

Highly adherent and compact copper coatings on steel substrates were successfully produced by electrodeposition using noncyanide bath based on glutamate as a complexing agent. The investigation was conducted using potentiodynamic cathodic polarization, cyclic voltammetry, in situ-anodic linear stripping voltammetry and chronoamperometry techniques. The results from the potentiodynamic cathodic polarization show polarization characterized by the presence of a current plateau (limiting current, i_lim) in the potential range -0.65 to -0.83 V_SCE, as a result of the deposition limitation by the diffusion process. The present glutamate bath has a higher cathodic current efficiency than that of cyanide baths. The electrochemical kinetic data confirms that the Tafel slopes of the solution containing glutamate ions are higher (821.1-849.9mVdecade^-1) than that without MSG (738.5mVdecade^-1). The relative invariance of α_c, observed for increasing glutamate ion concentrations, suggests that the Cu electrodeposition pathway is not affected by the presence of glutamate. However, the rate of Cu²⁺ deposition on the steel surface from glutamate bath, is much higher than that on the glassy carbon surface. Copper coatings with very different morphologies can be obtained from the glutamate bath by simply manipulating the applied current density. X-ray diffraction analysis and SEM observations revealed that monosodium glutamate (MSG) does not vary the texture of the electrodeposited copper. However, it depends greatly on the deposition parameters such as the applied current density, pH and bath temperature. High hardness of copper deposits was obtained both at low concentration of MSG and at low current density. Baths contained glutamate ions exhibited a slight decrease in the throwing power.