What causes small holes to appear after firing? Gas release from the material.
Right after painting, it looks beautiful, but after curing, small holes appear. The cause is not the paint, but the gases and moisture within the material. This explains the concept of "dry firing."
Right after application, it looks beautiful, but when taken out of the furnace, there are small holes lined up. This defect does not stop even when the paint is changed. ────────────── ■ Cause of Occurrence Inside castings and die casts, there are invisible cavities. The air or moisture trapped there expands with the heat of curing and breaks through the paint film. ■ Truth The holes open from the material side, not the surface of the paint film. If water from the pretreatment enters the cavities and is painted over before it dries completely, it will increase further. Even if the film thickness is increased to hide it, it will reoccur with each curing. ■ Improvement Measures Before painting, pre-bake the material at a temperature higher than the curing temperature to remove the gas first. It is also important to extend the drying time after washing to ensure no moisture remains in the cavities. Eiwa Kogei supports painting for all metals, including iron, aluminum, and zinc die casts. Please download the materials summarizing the confirmation points of the process for your use.
basic information
Defect: Pinholes. Management items: Material's pre-baking temperature and time, drying time after washing, curing temperature, film thickness.
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Applications/Examples of results
Aluminum die-cast parts, cast iron parts, and baked paint for welded structures. Selection of painting subcontractors, defect analysis by the quality assurance department, and training materials for new employees.
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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.