Common Issues in Caliper Coating: Cause Analysis, Prevention and Repair Solutions for Paint Peeling and Blistering

Common Issues in Caliper Coating: Cause Analysis, Prevention and Repair Solutions for Paint Peeling and Blistering

If issues like paint peeling and blistering occur after caliper coating, they not only affect the appearance but also render the protective function ineffective, leading to caliper rusting or performance degradation. Identifying the causes of these problems and implementing preventive and repair measures is crucial to ensuring a high-quality coating finish.

Paint peeling mostly stems from insufficient adhesion, with core causes focusing on three aspects: First, inadequate surface preparation – residual oil, rust, or uneven phosphating film on the caliper surface prevents the coating from adhering tightly. Especially for brake calipers, if residual brake fluid is not removed, it can easily cause the coating to peel off under high temperatures. Second, improper coating selection – for example, using room-temperature paint on high-temperature brake calipers. After high-temperature baking, the significant difference in thermal expansion coefficients between the coating and the substrate leads to peeling. Third, non-standard curing process – insufficient temperature or time results in incomplete curing of the coating, leading to low hardness and poor adhesion. Prevention should start from the source: during preparation, ensure the sandblasting roughness meets standards (Ra 50-80μm), the phosphating film is intact, and use a solvent to wipe and check for residual oil; select specialized coatings based on caliper type (high-temperature paint resistant to over 600°C for brake calipers); strictly control curing parameters as required by the coating (e.g., silicone paint requires curing at 180-220°C for 60 minutes). For repairs, completely scrape off the peeled coating, re-perform surface preparation, and then touch up the paint to avoid color differences and uneven adhesion caused by partial touch-ups.

Blistering is mainly caused by trapped gas or moisture in the coating, with common reasons including: Incomplete drying of the caliper after surface preparation – residual moisture on the surface evaporates when heated during curing, breaking through the coating to form blisters; excessive ambient humidity during spraying (relative humidity > 85%) – moisture in the air mixes into the wet film, or insufficient standing time after coating preparation leads to incomplete solvent evaporation; excessively thick coating (single spray coat over 80μm) – solvents in the underlying layer cannot escape in time and become trapped inside the coating. Preventive measures include: Ensuring the caliper drying temperature (60-80°C) and time (30 minutes) after preparation, and using a dew point meter to check surface moisture after cooling; choosing a spraying environment with humidity < 75%, and allowing two-component coatings to stand for 10-15 minutes after preparation before use; adopting a "thin coat, multiple passes" approach, controlling the thickness of each spray coat to 30-50μm, with a 20-minute interval between each pass. For small blisters, first sand the blistered area with fine sandpaper (800 grit), remove the damaged coating, and then touch up the paint; for dense blisters, the entire coating must be stripped off before re-coating to avoid residual hidden risks.