Evaluating Coating Adhesion Strength on Steel: Investigating the Impact of Distilled Water and Salt Solutions on Coating Performance

Abstract

This study evaluates the adhesion strength and electrochemical performance of two industrial coatings—Sigmashield 880 (light) and Simcoe 350 (dark)—applied to steel substrates and exposed to distilled water and acidic salt solutions over a four-week period. Six steel samples were prepared and categorized into two experimental groups: one treated with a zinc (Zn) inhibitor and hydrochloric acid, and another exposed to distilled water without inhibitor. Weekly monitoring of pH and voltage was conducted to assess electrochemical activity, followed by standardized pull-off tests to quantify coating adhesion strength. Results demonstrated that uninhibited samples exhibited significantly higher voltage readings and lower pH values, indicating elevated corrosion activity. Conversely, Zn-inhibited samples maintained lower and more stable electrochemical responses. Adhesion strength values ranged from 5 to 9 MPa, with the dark coating (Simcoe 350) without inhibitor achieving the highest value (9 MPa), while the light coating with inhibitor recorded the lowest (5 MPa). The findings underscore that while Zn inhibitors enhance electrochemical stability, final adhesion performance depends on complex interactions between coating composition, inhibitor compatibility, and environmental exposure. This research provides practical insights for optimizing protective coating systems in marine and industrial environments.