Impact of Acidic, Basic, and Corrosive Water Quality on Key Properties of Whitewash Coating at Elevated Temperatures

This study investigates the impact of chemically modified acidic, alkaline, and chloride‐containing coating systems on the mechanical, physical, and microstructural properties of whitewash coatings at elevated temperatures. The investigated coating is a commercial composite whitewash coating prepared by mixing white paint, white sealer, and wall putty in a volumetric ratio of 2:2.5:1, which is incorporated into standard, basic, acidic, and corrosive solutions and applied to cement mortar substrates prior to isochronal heat treatments up to 500°C. Comprehensive characterization, including hardness, density, compressive strength, frictional loss, CIELAB colorimetric analysis, optical microscopy, and scanning electron microscopy–energy‐dispersive X‐ray (SEM–EDX), was conducted to assess changes in properties. The findings indicate that the color of white coating samples remains stable up to 200°C, with significant thermal degradation occurring beyond this threshold, peaking at 300°C before diminishing due to chemical reactions and substance evaporation. Strength parameters such as hardness and compressive strength increase with temperature up to ~200°C, primarily due to the evaporation of free moisture and the resulting densification, which improves interparticle contact and yields a temporarily more compact, stable structure. However, beyond this temperature, strength declines as structural integrity deteriorates; progressive dehydration and degradation of the calcium‐rich mineral constituents and the polymeric binder system reduce the coating’s structural integrity. Normal water produces smoother surfaces, while heating to 400°C dislodges the whitewash coating. Chemical modification induces notable color transitions, microstructural cracking, and strength loss, with more severe deterioration under acidic and corrosive conditions than in basic modification. Acidic modification causes significant etching that weakens the coating system and leads to esthetic issues, while basic modification may induce cracks with less severity. Corrosive conditions primarily result in surface deterioration and crack development due to chemical decomposition.