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Surface roughness is important for improving adhesion, but being rough is not necessarily good. Excessive roughening can, on the contrary, lead to poor painting results. Particularly when the blasting pressure is too high, deep irregularities can form on the surface, preventing the paint from spreading evenly. As a result, air or solvents may remain trapped within the paint film, leading to pinholes or uneven film thickness. This is actually a point that is often overlooked. Excessive roughness affects not only adhesion failure but also appearance defects. Furthermore, it is common to manage blasting pressure at around 0.3 to 0.5 megapascals as a standard. Excessive projection can also lead to material deformation. A common misunderstanding in the field is the belief that "the rougher, the better the adhesion." By optimizing surface roughness, quality can often be stabilized. Actual improvement cases are also detailed in publicly available materials.

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Surface roughness is an important pre-treatment condition that affects the adhesion of the paint film. However, in the field, there are many cases where it is judged that "there is no problem because it looks nice." In reality, if the surface is too smooth, the paint may not penetrate sufficiently, leading to poor adhesion or peeling. This is especially significant with stainless steel and aluminum materials, where it may manifest as paint film lifting months later. This is actually a point that is often overlooked. Insufficient roughness can be difficult to assess visually. Furthermore, it is sometimes recommended to aim for a surface roughness of about Ra 1.0 to 2.0 micrometers before painting. Insufficient roughness increases the likelihood of pinholes and paint film peeling. A common misconception in the field is the belief that "a mirror finish is better." By managing surface roughness numerically, there are cases where adhesion can be greatly improved. Actual improvement cases are also detailed in publicly available materials.

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Even if the degreasing process is carried out properly, the quality of the paint can vary significantly due to subsequent management. The longer the time after degreasing that the surface of the parts is contaminated again with oil or dust, the lower the adhesion of the paint film will be. Time management from pre-treatment to painting is the key to preventing painting defects.

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Degreasing is an important process in the pre-painting stage that greatly affects the adhesion of the paint film. If the removal of oil, dust, and oxide films is insufficient, the adhesion of the paint film will decrease, leading to many defects such as paint peeling, pinholes, and variations in film thickness.

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## Defects in "Film Thickness Design": The Final Warning of Frequent Chipping Chipping in aluminum die-cast coatings is primarily caused by insufficient film thickness. Have you improved the coating design?

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## The Crisis of "Curing Management": The Truth Behind Frequent Curing Failures The main cause of curing failures in aluminum die-cast painting is insufficient curing. Have you checked the curing conditions?

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## Loss of "Chemical Treatment Function": Warning of Frequent Rust White rust on aluminum die castings is caused by the deterioration of the chemical treatment solution. Have you replaced the treatment solution?

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## Uncontrollable "Drying Conditions": The Risk of Gloss Unevenness Gloss unevenness in aluminum die-cast painting is primarily caused by drying temperature. Have you fundamentally improved the drying process?

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## The Failure of "Environmental Management": Warning of a Surge in Foreign Matter Contamination Environmental pollution from aluminum die-casting factories is causing an increase in foreign matter contamination. Is environmental improvement an urgent necessity?

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## Color Variation of "Film Thickness Variation": A Crisis of Quality Collapse Color variation in aluminum die-cast painting is caused by uneven film thickness. Are you able to check the spray pressure?

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## Breakdown of "Viscosity Management": Serious Situation of Frequent Dripping Dripping in aluminum die-cast painting is primarily caused by viscosity management. Have you conducted a review?

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## The Limits of "Baking Temperature": The True Culprit Behind the Sudden Increase in Blisters Blisters in aluminum die-cast coatings are primarily caused by baking conditions. Have you checked the process?

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## The Truth Behind the Frequent Occurrence of Pinholes Caused by "Internal Gas Expansion" in Aluminum Die Casting. Is the Burnout Treatment Sufficient?

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## "Porosity during casting" is the cause of poor adhesion: Urgent measures are needed. Poor adhesion in aluminum die-cast coatings is caused by gas porosity. Have you implemented fundamental countermeasures?

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In products that combine different metals, pinholes may occur due to differences in thermal expansion. During curing, the amount of expansion varies by material, leading to stress within the coating. Particularly in combinations with a large difference in expansion coefficients, such as aluminum and iron, there can be cases of fine coating failure. Effective countermeasures include using low-temperature curing paints and designing highly flexible coatings. It is also important to consider these factors from the structural design stage. Detailed examples of improvements are also provided in publicly available materials.

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In aluminum anodizing, the sealing treatment conditions can affect the occurrence of pinholes. Insufficient sealing may leave internal voids that can gasify during baking. Conversely, excessive sealing can reduce paint adhesion, potentially leading to localized coating defects. As a countermeasure, it is important to align the sealing conditions with the painting specifications. Additionally, using a dedicated primer may improve adhesion. Detailed examples of improvements are also provided in publicly available materials.

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In molten zinc-coated materials, gas generation due to surface reactions can sometimes cause pinholes. Particularly when the coating surface is too smooth, solvents in the paint can become trapped. Additionally, if white rust or surface contamination remains, reactions can progress during curing, leading to the formation of holes in the coating. Effective countermeasures include sweep blasting and the use of specialized primers. Thickness management is also important, as care must be taken to avoid solvent entrapment due to excessive coating thickness. Detailed examples of improvements are also provided in publicly available documents.

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Copper materials have a characteristic of rapid oxidation, making them prone to pinhole formation. If left uncoated for a long time after polishing, an oxide film forms, which reduces the adhesion of the coating. In particular, in high humidity environments, the oxidation reaction accelerates, and there are cases where gasification occurs during baking. Even if the appearance is clean, surface reactions are still progressing. As countermeasures, it is important to paint immediately after polishing and to shorten storage time. Additionally, managing air blowing after degreasing also affects adhesion. We provide detailed examples of improvements in copper materials in publicly available documents.

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Pinholes that occur in die-cast materials are primarily caused by internal gases. When heated, the internal gases expand and break through the coating, creating holes. The occurrence rate is particularly high in materials with many voids or gas entrapment during casting. It is often characterized by the fact that treating only the surface does not lead to improvement. As a countermeasure, a baking treatment at 200 to 250°C for about 30 to 60 minutes is effective. Additionally, using low-temperature curing coatings may also help reduce occurrences. Detailed examples of improvements are also introduced in publicly available materials.

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Stainless steel is a material that is resistant to rust but difficult for paint to adhere to. The passive film on the surface can repel paint, leading to pinholes. Particularly, when there is insufficient polishing or poor degreasing, voids can easily form within the paint film. Additionally, if the film thickness is too great, solvents may not escape properly, resulting in holes. Effective countermeasures include the use of sandblasting or specialized primers. In some cases, a surface roughness of around Ra 1.0 to 2.0 μm is recommended. We also provide detailed examples of improvements in publicly available materials.

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Pinhole formation in brass can be caused by surface changes due to oxidation reactions. Over time after polishing, an oxide film forms and adhesion decreases. The reaction is particularly prone to progress due to insufficient degreasing or humidity during storage. During baking, fine gases may be generated, leading to the formation of holes within the coating. Measures to address this include immediate painting after polishing and managing oxidation suppression. Additionally, incorporating a weak acid wash may improve adhesion. Detailed examples of improvements are also provided in publicly available materials.

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Pinhole defects in iron materials can sometimes be caused by fine red rust. If there is hidden corrosion on the surface, gases or moisture can be generated during the curing process, which can destroy the paint film. Special attention is needed for cases of insufficient shot blasting or re-rusting due to prolonged exposure after degreasing. Condensation caused by temperature differences can also have an impact, and the frequency of occurrence tends to increase in winter. As countermeasures, painting within four hours after blasting and using anti-rust primers are effective. Humidity management is also important, with cases recommending levels below 60%. We also provide detailed examples of improvements specific to iron materials in publicly available documents.

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Pinholes that occur in galvanized materials can sometimes be caused by gas generation due to surface reactions. Particularly when white rust is present, reactions can progress during baking, leading to gas formation inside the paint film. The zinc surface is prone to reacting with moisture, so materials that have been stored for a long time require extra caution. Additionally, insufficient zinc phosphate treatment can lead to reduced adhesion and the expansion of pinholes. As a countermeasure, it is important to combine light polishing with chemical treatment. Especially in environments with humidity over 60%, the progression of white rust accelerates, making proper storage management necessary. Detailed examples of improvements are also provided in publicly available materials.

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Pinholes that occur in aluminum products can sometimes be caused by moisture remaining on the surface or inside the material. Special attention is needed, particularly after machining or insufficient drying following cleaning. During baking, moisture evaporates and can push up the coating, resulting in tiny holes. Aluminum has a high thermal conductivity, causing the surface temperature to rise rapidly, which can prevent internal moisture from escaping. The risk of occurrence increases, especially with a film thickness of 40μm or more. Measures to address this include pre-drying at 60-80°C and managing the storage environment before painting. Additionally, care must be taken to prevent moisture re-adhesion in environments with humidity above 70%. We also provide detailed examples of improvements specific to aluminum materials in our published materials.

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In products that combine dissimilar metals, delamination can occur. The thermal expansion rates differ for each material. Distortion can occur during baking or in the usage environment, putting stress on the coating. It is important to consider structural design as well. We also provide detailed information on improvement cases in publicly available materials.

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The sealing treatment conditions for aluminum alloy materials affect adhesion. After sealing treatment, paint may become difficult to adhere. There are cases where additional polishing or specialized primer treatment is applied. A painting design that matches the treatment conditions is necessary. We also provide detailed examples of improvements in publicly available materials.

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Hot-dip galvanized steel is a material that is difficult for paint to adhere to. It has a very smooth surface, making it challenging for the paint film to stick. There may be cases where sweep blasting or specialized surface treatment is necessary. Designing specialized processes is important. We also provide detailed examples of improvements in publicly available materials.

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Copper oxidizes quickly and is a material that is prone to paint peeling. Oxidation begins immediately after polishing. Prolonged exposure after degreasing reduces adhesion. Managing process time is important. Speed management specific to copper is crucial. We provide detailed examples of improvements in publicly available materials.

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In die-cast materials, internal gas can cause paint peeling. Internal gas expands during heating. A baking treatment at 200 to 250°C can be effective in some cases. Measures that consider the interior of the material are necessary. We also provide detailed examples of improvements in publicly available documents.

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Stainless steel has high corrosion resistance, but it is a material that is difficult for paint to adhere to. There are cases where the passive film on the surface repels the coating. Sandblasting or a special primer may be required. Pre-treatment specifically for stainless steel is important. We also provide detailed examples of improvements in publicly available materials.

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Brass is prone to oxidation in the air, and as it discolors, the adhesion of the coating decreases. Even if the surface discoloration is slight, the reaction is still progressing. Poor adhesion can occur due to insufficient degreasing or residual oxide film. Immediate painting after polishing is important. Specific management for brass is required. We also provide detailed examples of improvements in publicly available materials.

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Many of the causes of paint peeling on iron materials are due to red rust. When surface corrosion progresses, the paint film cannot adhere properly. Even fine rust can lead to corrosion beneath the paint film. If blast treatment or rust prevention primer is omitted, peeling can occur within a few months. Proper substrate treatment is particularly important for iron materials. We also provide detailed examples of improvements in publicly available documents.

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One of the causes of paint peeling on galvanized materials is white rust. When white rust occurs, it becomes difficult for the paint film to adhere. Even immediately after galvanizing, reaction products are present on the surface. If zinc phosphate treatment or light polishing is not performed, the paint film is likely to lift. A storage environment with high humidity is also dangerous. Specific measures for galvanized materials are necessary. We also provide detailed examples of improvements in publicly available documents.

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One of the causes of paint peeling in aluminum products is the oxide film that forms on the surface. Aluminum oxidizes simply by being exposed to air, which hinders the adhesion of the paint film. Even if the surface appears clean, a thin oxide film is formed. If acid cleaning or chemical treatment is not performed, the adhesion significantly decreases. This is especially important for materials that have been stored for a long time. In actual practice, the results can vary greatly depending on the condition of the material. We also provide detailed examples of improvements in aluminum peeling in publicly available materials.

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Chipping is caused by a 'lack of adhesion': The impact resistance is not determined solely by the strength of the coating. If the adhesion is low, the coating will rebound and peel off upon impact. Even a hard coating that appears sturdy is meaningless if its adhesion to the substrate is weak. Furthermore, there are more complex issues: insufficient pretreatment, differences in the expansion coefficients of materials, inadequate coating thickness... all of these affect chipping. A simple notion of a 'hard coating' cannot provide an essential solution.

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Searching for the culprit of poor curing: Temperature? Time? Or the mixture? In fact, these three work as a "trinity." Simply having a high drying temperature is not enough. There is a necessary heating time. Furthermore, if the mixture of the paint (the ratio of the main agent to the hardener) is not accurate, no matter how much you heat it, it will not fully cure. In many situations, the mixture is underestimated as "not a big deal," but this is the biggest pitfall.

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The recurrence of rust is the "price of forgetting the pre-treatment." There are cases where rust reappears a few months after painting. The cause lies hidden in the tiny, invisible dents on the surface. If the chemical treatment is incomplete, moisture remains in the micropores of the material. Even if coated with anti-corrosive paint, corrosion from within cannot be prevented. Many companies mistakenly believe that "it's okay because the paint film is thick." However, the anti-corrosive performance is determined by the "substrate."

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The true nature of gloss unevenness is "subtle changes in drying temperature." Even if they appear to be the same drying oven, the temperature distribution varies by location. Additionally, the outside temperature changes with the season and time of day, causing slight deviations in drying conditions. Furthermore, another complicating factor is that the curing speed differs even at the same temperature, depending on the thickness and color of the coating film. To achieve uniform gloss, it is essential to adjust not only temperature management but also drying time, film thickness, material properties, and other complex factors.

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The true culprit of foreign matter contamination is the "invisible enemy." The dust in the painting booth cannot be detected by the naked eye. Old paint particles accumulate in areas with poor air flow and in the corners of equipment. Even if you think the cleaning is thorough, contamination exists at the microscopic level. However, this is important: environmental management alone is insufficient. The filters in the paint supply line, the air quality of the spray gun, and the negative pressure management of the painting booth... only when all of these are integrated can foreign matter contamination be prevented.

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The true culprit of color unevenness is "variability in film thickness." Color development is directly linked to film thickness. Even with the same color, if the film thickness varies by 10%, it will appear as if the "color is different." Why does film thickness vary? It is due to almost unconscious changes in application conditions (distance, speed, pressure). In the case of non-mechanized hand painting, even if the same person is painting, it can differ depending on the day, time of day, and posture. Without standardization, achieving consistent quality is impossible.

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The reason why drips are unstoppable lies in the "betrayal of viscosity." Viscosity adjustment often relies on experience and intuition, which is dangerous. Factors such as paint temperature, type of thinner, humidity, and spray pressure all affect viscosity. Even if applied at the optimal viscosity, if the spray distance is incorrect, the film thickness will be uneven, leading to drips. Many companies settle for the simple solution of "increasing viscosity." However, the true cause is the "harmony of the entire system."

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Blistering defects: What is happening inside the coating? It is actually an "attack of moisture and gas." The moisture inside the material is not visible. In the case of die casting, moisture is absorbed into the fine pores of the mold. When heated, that moisture expands and lifts the coating. This is why pre-baking treatment is effective. However, many companies do not understand this true cause. Gradual drying according to the characteristics of the material is essential.

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The true nature of pinholes is "a state where bubbles have lost their escape route." Why do bubbles occur during painting? The main causes are the rapid evaporation of solvents and gas generation. However, it is not that simple. If the film thickness is too thick, the internal gas does not have enough time to reach the surface, and bubbles become trapped within the coating. If the drying temperature is too high, it is also problematic. If it is too low, that is also an issue. Finding this "optimal value" is the key to eliminating pinholes.

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The true culprit behind paint peeling lies in "laziness in pre-treatment." 90% of defects that manifest as poor adhesion are actually determined at the pre-treatment stage. Inadequate degreasing can hinder paint adhesion due to even a slight amount of oil. However, here is the crucial point: oil is not the only culprit. Residual moisture, neglecting oxidation films, and errors in drying timing are all intertwined factors.

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Improvement methods for insufficient adhesion, coating strength, and substrate treatment that cause paint chipping. Insufficient adhesion reduces impact resistance. A hard coating alone is not enough; design is important. We have published case study materials on improvements. Please take a look.

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