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The failure process of heavy anti-corrosion paint is usually a progressive damage, going through five stages from microscopic penetration to macroscopic damage.: Blistering → rust → coating detachment → pitting → loss of structure. Blistering: Moisture and oxygen penetrate into the metal interface through the pores or defects of the coating, forming local pressure under the temperature difference or electrochemical action, causing the coating to bulge to form bubbles. If cathodic protection is excessive, hydrogen evolution may also cause blistering. Corrosion Initiation: The metal substrate under the bubble begins to react electrochemically with water and oxygen to generate rust (Fe₂O₃·nH₂O). The volume of corrosion products expands, further pushing the coating to bulge and accelerating the decline in adhesion. Coating Delamination: As corrosion spreads, the bonding force between the coating and the metal is destroyed, resulting in peeling, delamination or edge peeling. It is more likely to occur especially when the surface treatment is poor (such as salt residue >5μg/cm²) or the compatibility between coatings is poor. Pitting Corrosion: Corrosion is concentrated in local areas to form deep holes, penetrating metal cross-sections, making it extremely difficult to detect and highly destructive. It is common in stress concentration areas such as welds and edges, eventually leading to structural damage. Structural Failure: Large-area corrosion and coating failure reduce the metal's load-bearing capacity, leading to serious consequences such as perforation and fracture, which affect the safe operation of the equipment and require overhaul or replacement. The entire process is affected by environmental factors (such as ocean atmosphere, strong acid and alkali), improper material selection (such as non-alkali-resistant epoxy used in alkali environments) and construction defects (such as insufficient coating thickness and substandard surface roughness).