Steel surface preparation prior to painting and its impact on protective performance of organic coating

•Five surface preparation methods were studied to prepare steel prior to painting.•Steel surface was analytically and morphologically characterized.•Anti-corrosion performance was evaluated by DC resistance and pull-off methods.•UHP hydroblasting was determined as an optimum method with best performance.•DC resistance showed high sensitivity to local degradation unlike adhesion level. The influence of surface preparation on performance of alkyd coatings on steel was investigated. Degreasing, abrasion with emery, acid pickling, hydroblasting and wet abrasive blasting methods were used to modify the surface of steel before painting. Steel surfaces were analytically and morphologically characterized before painting. DC resistance and pull-off adhesion methods were used to evaluate the performance of alkyd coatings on differently prepared surfaces. Results implied the key role of oxide layer in maintaining the high level of corrosion protection. Also the detrimental influence of the inherent contamination caused by wet abrasive blasting method was shown as a cause of early failure of protective properties. Comparison between electrochemical and adhesion results showed that they may not indicate towards similar directions in terms of protective properties which is due to the different factors affecting them.