Study on The Behavior of Light on Erosion in Epoxy Coating on SS316L

Abstract

This research employs optical analysis, and light intensity analysis with, three coating systems—pure epoxy, epoxy with 0.1 wt.% graphene, and epoxy with 1 wt.% graphene—were systematically evaluated for their erosion resistance and optical characteristics on SS316L stainless steel substrates. The coating thicknesses ranged from 85 µm to 103 µm, with erosion factor calculated as the reduction from the maximum thickness (103 µm). Pure epoxy exhibited the highest erosion factor of 18 µm, followed by 11 µm for epoxy + 0.1% graphene, and as low as 5 µm for epoxy + 1% graphene, indicating improved erosion resistance with increasing graphene content. Surface roughness (Ra) measurements showed a corresponding rise due to erosion, increasing from approximately 0.33 µm to 1.12 µm for pure epoxy, whereas the increase was limited from 0.19 µm to 0.45 µm in epoxy + 1% graphene coatings, highlighting the protective advantage of graphene modification. Optical analysis using RGB light filters further revealed a progressive increase in deviation values with erosion severity, where pure epoxy exhibited a maximum deviation of 0.165 at highest erosion, compared to only 0.025 for epoxy + 0.1% graphene and 0.008 for epoxy + 1% graphene at lower erosion levels. Additionally, the Energy Index (Ep), sensitive to nanoscale surface roughness, demonstrated a strong inverse correlation with Ra (Pearson Linear Correlation Coefficient, PLCC = 0.91; Mean Absolute Error, MAE = 10.7 nm), while the Structural Color Aliasing Index (SCY) effectively captured macro-level degradation, showing higher correlation (PLCC = 0.93) and a MAE of 0.12 µm. These findings not only confirm the erosion mitigation capability of graphene-reinforced coatings but also establish a robust foundation for non-destructive, real time optical monitoring of coating health using structured light and digital image-based metrics.