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Phosphating is a surface treatment process widely used for preparing metal surfaces before painting. The phosphate coating plays a very important role in enhancing after-painting corrosion resistance, which is one of the essential quality requirements of painted surfaces. Continued research and development is therefore under way in various parts of the world to increase the corrosion resistance enhancement effect of phosphating. Moreover, because the demand for environmental protection has been increasing in recent years, reducing the amount of waste (sludge) generated during the phosphating process is also strongly required. To meet these requirements, we have developed a novel phosphating technology called the “electrolytic phosphating process,” which drastically enhances corrosion resistance after painting and reduces sludge generation. The developed process has already been put to practical use for surface preparation before cation electrodeposition painting of automotive parts.

Evaporator surface treatment technology is important for air conditioners in that it provides resistance to rust, odor and bacteria, while imparting hydrophilicity. However, since the first-layer chromate coating contains hexavalent chromium, an environmental loading substance whose stricter regulation is under consideration, development of an alternative technology is needed. We selected titanium coating for the first-layer non-chromate coating, and added an inhibitor to the second-layer multifunctional resin coating to impart a self-healing effect without undermining the other functions. As a result, we succeeded in developing a non-chromate surface technology that ensures the same level of rust resistance and other qualities as with conventional technology.

Among aluminum heat exchangers used for automotive air conditioning, the evaporator is located in the instrument panel. We have developed a new evaporator by: 1) improving the heat transfer performance through use of thinner tubes and fins; 2) establishing technologies for improving corrosion resistance and enabling reduction in wall thickness (development of highly corrosion-resistant material and control of Zn diffusion by shortening brazing time); and 3) improving refrigerant distribution in the tanks. The new evaporator is equivalent to our conventional MS Evaporator (of Multi-Tank Super-Slim Structure)(1) in cooling performance and corrosion resistance, while being significantly thinner (35% reduction) and lighter in weight (40% reduction).