The cause of rust reoccurrence is the thinness of the chemical treatment film. Ensuring a thickness of 8-12 microns allows for 5 years of corrosion resistance.
Reoccurrence of rust is a phenomenon where rust occurs beneath the paint film 3 to 6 months after painting, causing the paint film to swell. This is particularly common in pressed and cast products, and if it leads to a return claim within the quality assurance period, the cost for replacement or repair amounts to 150,000 to 250,000 yen per case. Importance of conversion coating thickness: When managing the conversion coating at 5 microns, 15-20 percent rust reoccurrence occurs within 2 years. If the thickness is increased to 8-10 microns, the rust reoccurrence rate during the same period is reduced to below 2 percent. Crystal structure of phosphate treatment: The larger the crystals in the conversion treatment, the higher the corrosion resistance. By managing the crystal diameter between 5-15 microns, it is possible to clear 1000 hours in the salt spray test (JIS Z 2371). Combination effect with pretreatment: Optimizing the three stages of degreasing, oxide film removal, and conversion treatment improves corrosion resistance by more than three times compared to just conversion treatment alone. Similar measures are necessary even for stainless materials. Our company manages the conversion coating thickness within plus or minus 1 micron and offers a 5-year rust-free guarantee. We have also achieved no rust generation even after 1500 hours in the salt spray test.
