The electrodeposition of cobalt from sulphate solutions containing boric acid was investigated using EQCM technique coupled with potentiostatic measurements. The boric acid was added to electrolyte as a buffer to avoid the local pH rise caused by parallel hydrogen evolution reaction (HER). The results showed that the buffer contribution of boric acid is effective in the cobalt electrodeposition at 25 degrees C; however, cobalt hydroxide is formed simultaneously with cobalt deposition at 48 degrees C. The M/z values calculated using the Sauerbrey equation and the Faraday Law showed that in the initial stages of deposition at 48 degrees C, only cobalt deposits were detected, but after 2 s, an important amount of Co(OH)(2) started to be formed. (c) 2007 Elsevier Ltd. All rights reserved.