The long-term stability of NiCoZn coating for hydrogen evolution reaction (HER) was investigated in 1 M KOH solution under 100 mA cm(-2) current density at room temperature. The effect of electrolysis on the corrosion behavior of NiCoZn coating was also studied. The alloy prepared on a copper electrode (Cu/NiCoZn) was etched in a concentrated alkaline solution (30% NaOH) to produce a porous and electrocatalytic surface suitable for use in the HER. The bulk and surface compositions of coating before and after alkaline leaching were determined by atomic absorption spectroscopy (AAS) and energy dispersive X-ray (EDX) analysis. The surface morphologies of freshly prepared and aged electrodes were investigated by scanning electron microscopy (SEM). Their catalytic activity towards the HER was assessed by recording cathodic current-potential curves and electrochemical impedance spectroscopy (EIS) techniques. It was found that the NiCoZn coating has a compact and porous structure. The long-term operation at 100 mA cm(-2) current density showed that the electrochemical activity of Cu/NiCoZn electrode increased slightly with increasing electrolysis time. The activation of electrode related to the removal of any existing corrosion products and accumulations from the pores and formation of cracks during hydrogen gas evolution. The corrosion tests showed that the corrosion resistance of Cu/NiCoZn electrode changed after electrolysis. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.