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This work focuses on the effect of surface roughness, morphology and chemistry on the initial adhesion strength and corrosive de-adhesion properties of adhesive bonds. Steel surfaces are subjected to different surface pre-treatment methods such as mechanical abrasion, grit blasting, zirconium conversion treatment and silane treatment. Single-lap joint tests were performed to assess the initial bond strengths. Static wedge tests were used to study the loaded environmental ageing of joints and unloaded delamination of adhesive films from the steel surface was studied by means of scanning Kelvin probe (SKP). Experimental results indicate surface roughening plays an important role on the initial adhesion but a minor role in the durability of the bonded steel. The improved initial adhesion is mainly attributed to the increased interfacial bond area at higher surface roughness whereas complex morphology shows a more profound effect on both the initial adhesion and the durability of the interfacial adhesion. In the absence of complex texture, surfaces with altered chemistry by zirconium-or silane treatment exhibit a significant increase of the initial bonding strength and assessment of the interfacial delamination kinetics by SKP reveal that despite the absence of any surface topography, these surfaces prove to have higher resistance to delamination.

Effect of phosphate ions on electrochemical behaviour of copper in sulphate solutionsT he eVect of phosphate ions on the corrosion behaviour of copper in sulphate solutions was G. KILINÇ Ç EKER investigated at diVerent temperatures ( 293, 313, 333, and 353 K) and at diVerent pH values B. YAZICI (pH =2·1, 7·2, and 12·3) . A three electrode electrochemical technique was used for the A. B. YILMAZ measurements, using a saturated calomel electrode ( SCE) for reference purposes. Both M. ERBIL anodic and cathodic polarisation curves were established, f rom which the anodic and cathodic T afel constants were determined. Corrosion potentials were determined by ex trapolation of the anodic and cathodic T afel lines to the point of zero current density. T he results showed that for a pH value of 2·1, the corrosion rate of copper showed a marked tendency to increase with increasing temperature in solutions containing either sulphate alone or sulphate plus phosphate. H owever, at pH values of 7·2 and 12·3, this tendency became less pronounced in solutions containing sulphate alone and in solutions containing sulphate plus phosphate together, max imum corrosion rates were greatly reduced and showed less tendency to increase with increasing temperature. A nodic and cathodic reaction mechanisms are proposed to explain the observations for the corrosion of copper.

One of the main applications of SVET in corrosion research is the study of the corrosion inhibition effectiveness and the evaluation of the self-healing effect of inhibitor-containing coatings. The tip of the platinum/iridium vibrating electrode is electroplated with black platinum, which creates a large electrode surface and confers high capacitance to the tip. When studying organic inhibitors in aqueous solutions with SVET, inhibitor adsorption may occur at the tip, causing its contamination and the initial calibration conditions of the system might not be valid. This may lead to an incorrect interpretation of the results. This work is intended to study the effect of different inhibitors (cerium nitrate, 8-hydroxyquinoline, potassium 2,5-dimercapto-1,3,4thiadiazolate, benzotriazole and mercaptobenzothiazole), typically used for corrosion protection of aluminum alloys, on the Pt probe signal during SVET measurements. The results reveal the detrimental effect of some corrosion inhibitors on the sensitivity of the vibrating probe, an effect that imposes a regular assessment of the electrode state during measurements. The increase of the signal noise was related to a decrease of the probe capacitance, while the false current density signal was a result of the potential drift between vibrating and reference electrodes.

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