Epoxy coatings are widely used in industrial corrosion protection, but the issue of cross-cut blistering under salt spray conditions has long plagued the industry. Recent studies show that this phenomenon results from the combined effects of "water-oxygen-ion" triad corrosion and internal stress within the coating film. After extensive experimentation and field validation, a team of coating technology engineers has developed a five-step closed-loop solution, successfully extending the onset time of epoxy coating cross-cut blistering from 200 hours to over 800 hours, meeting the stringent requirements of C5-M environments.

      Regarding root causes, exposed steel at scratch sites acts as an anode, undergoing oxidation to form soluble ferrous chloride. Cathodic reactions beneath the surrounding coating elevate the local pH to above 11; the resulting alkaline environment hydrolyzes epoxy ester bonds. Coupled with a 3–6 fold volume expansion of corrosion products, this ultimately lifts the coating to form "alkaline blisters." High permeability of the coating to water and oxygen further accelerates blister growth.

     To address this issue, the solution targets five key areas: first, increasing coating thickness to over 90μm and incorporating 5%–8% flake-shaped fillers and 0.5%–1% nano-SiO₂ to significantly reduce permeation rates; second, raising primer solids content to over 70% and adding compounded phosphates and cross-linking agents to suppress alkali generation; third, introducing non-silicone polymeric defoamers and optimizing solvent systems and curing processes to create channels for bubble escape; fourth, strictly controlling substrate preparation standards, achieving a blast-cleaning grade of Sa2.5 or higher, ensuring construction conditions meet specifications; fifth, standardizing the cross-cut test procedure to ensure testing accuracy.

     Implementation of this solution will greatly extend the service life of epoxy coatings in harsh environments such as marine and chemical industries, providing technical support to reduce maintenance costs across related sectors.


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