What causes the paint to peel from the corners of the parts? Insufficient film thickness at the corners.
While flat surfaces are not an issue, paint peels off from the edges of corners and holes, causing rust to spread. This explains the reasons for the thinning of the coating at corners and the countermeasures that can be taken through deburring and chamfering.
The flat surfaces are clean, but the paint is peeling from the edges of corners and holes, allowing rust to spread from there. Even if you repaint, doesn't it start again from the same places? 【First, please look here】 □ Peeling is concentrated at the edges of corners, holes, and cut surfaces → Insufficient film thickness at corners □ Burrs or sharp edges remain at corners → Paint does not adhere well □ Peeling areas are rusted → The base material is damaged 【Why does it happen?】 Paint shrinks due to surface tension while drying, escaping from sharp corners. Therefore, even if the film thickness on flat surfaces is sufficient, the corners become significantly thinner. Additionally, the edges cut by lasers or shears are less effective for pre-treatment. 【Countermeasures you can implement starting today】 1. After deburring, add a small roundness (chamfer) to the corners. 2. Measure and record the film thickness at the corners separately from the flat surfaces. 3. For parts with many corners, reconsider the primer and the number of coats. 【Free materials】 Methods to identify causes from the way paint peels are explained in "Eiwa Kogei_Painting Trouble Introduction_Identification and Countermeasure Guide."
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Subject: Powder coating of sheet metal products made of iron, stainless steel, and aluminum / Inspection items: Deburring and chamfering, film thickness at corners, surface treatment of edges.
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Measures against paint peeling and rust starting from the edges of corners and holes of sheet metal, press, and cutting processed products, and education on chamfering instructions during the design phase.
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We are not just a "subcontracted painting factory." Established in 1958, our company has a foundation of painting technology and also specializes in chemical treatment, stripping, and cleaning, functioning as the "external surface treatment department" in your organizational chart. Based on our philosophy of "preparation is eight-tenths of the work," we emphasize participation from the "upstream process" before the drawings are finalized. We conduct test painting on a wide range of metals and difficult materials, and we produce the entire process from assembly, packaging, to delivery, thereby reducing your management workload. Additionally, by being able to perform zinc phosphate treatment in-house, we achieve stable painting quality. Furthermore, our micro-heating stripping technology, which does not use chemicals, maintains the electrical state of the "jigs (hangers)" that influence painting quality. Our approach of "pre-treatment determines painting quality" ensures the stability of the paint film during mass production. Rather than simply "applying specified standards," we work backwards to achieve optimal painting specifications and prevent scratches during transportation, sparing no effort in thorough discussions from the outset. This diligent preparation is the shortest path to preventing rework and minimizing total costs. From the development stage, please utilize the expertise of our specialists as part of your production line.