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Abstract
The effects of blasting with metallic steel grit and non-metallic alumina grit on steel surface characteristics were evaluated. These abrasives are generally used at construction sites and in vacuum blasting. Milled steel specimens were used to investigate the effect of the blasting conditions on surface properties. The effect of difference in surface properties on the adhesion strength and corrosion behavior were measured through adhesion tests, polarization curves, and electrochemical impedance spectroscopy. The limitations of blasting were evaluated using corroded steel specimens, as were the effects of corrosion products, salts, and abrasive material remaining on the blasted steel surface on the adhesion and corrosion resistance of paint. Steel grit more effectively increased the surface roughness than alumina grit; however, with both abrasive materials, the roughness increased with the blast projection angle. However, in the case of alumina grit, some abrasive material remained on the surface; thus, the actual roughness not including the residual abrasive material was more complex and greater than that of the sample blasted with steel grit. According to the adhesion strength test of painted and unpainted specimens, the adhesion force improved with increasing surface roughness and residual abrasive materials. Further, surface roughness was linearly correlated with the adhesion strength of unpainted specimens for both abrasive materials with blasting, and the adhesion strength force with alumina grit was approximately 1.4 times higher than that with steel grit, suggesting that increased roughness and residual abrasive material could benefit adhesion. According to the electrochemical test results, lower roughness and increased residual abrasive material owing to alumina grit on the steel surface enhanced the surface corrosion resistance, confirming the benefit of residual materials. Grinding left behind corrosion products and salts under the steel, resulting in the recurrence of rusting. However, the residue from blasting with alumina suppressed corrosion, thus improving the adhesion and corrosion resistance of the paint.
Highlights
Introduction iationsTo maintain bridges and other steel structures, surface treatments are generally applied before painting to remove impurities from steel surfaces and impart appropriate roughness [1]
Many cases have been reported wherein moisture penetrates the coating owing to osmotic pressure and early corrosion occurs under the coating when salt remains on the steel surface because of insufficient surface treatment before painting [4]
In the case of MST, irregular roughness features caused by plastic deformation were observed on the steel surface, as shown i features caused by plastic were was observed onto thebesteel surface, as shown
Summary
The abrasive, blast pressure, abrasive projection angle, and distance were adopted according to the conditions generally used at new constructions sites and those in need of serviced sites. The nozzle and specimen were fixed and blasted for 5 s with a blast pressure of 0.7 MPa, an abrasive projection rate of, 3.83 L/min, an angle of 60◦ from the horizontal, and a distance to the subject of 300 mm. The following steel plates cleaned by both abrasive blasting were hen characterized in terms of surface roughness to examine the effects of blasting residue:.
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