Improve the corrosion resistance of electro-galvanized and hot-dip galvanized surfaces

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Regarding the surface treatment of fasteners such as screws, bolts, and nuts, two main factors are taken into consideration: 1. salt spray resistance (to prevent rusting) and 2. film thickness (to ensure proper fitting). The traditional method involves electro-galvanizing followed by passivation; the salt spray test lasts around 100 hours. Hexavalent chromium contained in the passivation solution is considered a pollutant, which puts significant pressure under environmental regulations. Hot-dip galvanizing + passivation: as long as the film thickness is sufficient, the salt spray resistance can reach up to 500 hours. However, an excessive film thickness can affect the fit of the fasteners. At the same time, there are also various constraints such as environmental protection issues. The currently popular treatment process is electro-galvanizing followed by a Raspat coating; a total film thickness of 15–18 μm is sufficient to achieve performance equivalent to SST1000 hours or more. This coating has a good adhesion to electro-galvanized layers. Unlike Dacromet, it is a completely chromium-free, environmentally friendly coating that complies with environmental regulations such as REACH and ROHS. It also features color-adjustability, resistance to acids and alkalis, and resistance to electrical corrosion. It currently has a wide range of application records in industries such as construction, automotive, wind power, and railways. High cost-performance, more professional surface treatment technologies, reliable and stable processing services along with technical support