THE EFFECTIVENESS OF TEA CO2-LASER ABLATION FOR THE TREATMENT OF HOT DIPPED GALVANIZED MILD-STEEL PRIOR TO ADHESIVE BONDING

TEA CO2-laser ablation has been studied to establish its effectiveness for the cleaning of hot dipped galvanised (HDG) mild steel. This lase r-based process was demonstrated to be more effective than double-degr easing for the removal of organic contamination from a previously oily surface. In addition, the TEA CO2-laser was shown to modify both the near surface chemistry and the topography; the precise modifications b eing dependent upon the degree of treatment used. In bond durability t rials, the changes introduced to the laser-treated HDG surface were sh own to provide equivalent or better joints compared with degreased adh erends. In the same durability trials, a commercially-available phosph ate-based, wet chemical treatment was shown to provide bond durability significantly inferior lo the TEA CO2-laser. In contrast, a chromate- based process gave markedly superior bond durability. Possible explana tions for the bond test results have been given.