Analisis Daya Lekat Sistem Duplex Coating Pada Baja Karbon Galvanis Dengan Variasi Persiapan Permukaan Berdasarkan Standar NORSOK M-501 Dan ISO 12944

Abstract

Corrosion is one of the main causes of reduced service life of steel structures in marine environments, making effective protection systems essential. One commonly used method is a duplex coating system, which combines a hot-dip galvanizing (HDG) layer with an organic coating. The performance of this system is strongly influenced by the quality of surface preparation, as it contributes to improving adhesion strength through the mechanical interlocking mechanism. This study aims to analyze the effect of variations in surface preparation methods on the adhesion strength of a duplex coating system applied to galvanized ASTM A36 carbon steel. The surface preparation methods consisted of non-blasting (solvent cleaning), sweep blasting, and grit blasting. The coating system used a two-coat system consisting of an epoxy primer (Penguard Primer) and a polyurethane topcoat (Hardtop AX), with a dry film thickness (DFT) ranging from 140–150 µm. The surface preparation procedures and test evaluation were conducted with reference to the NORSOK M-501 standard, while the coating system referred to ISO 12944-5 for corrosivity categories C3 to C4. Adhesion strength was evaluated using the pull-off test method in accordance with ASTM D4541 and ISO 4624. The results showed that the grit blasting method produced the highest surface roughness and adhesion strength compared with sweep blasting and non-blasting methods. All specimens met the minimum adhesion strength requirement of 5 MPa specified by NORSOK M-501. The failure mode identification also showed that the specimens prepared using grit blasting were predominantly characterized by cohesive failure, indicating better coating bond quality compared with the other surface preparation methods. Therefore, grit blasting is recommended as the most optimal surface preparation method for improving the adhesion strength of the duplex coating system on galvanized carbon steel.