What standards should be met for the corrosion resistance test of the metal lighting electrical ready board body?

The metal lighting electrical ready board body in the African region (including rural power grid project) is corrosion-resistant, mainly based on the general requirements for low-voltage switchgear and control equipment shell bodies in GB/T 20641-2014 (IEC 62208). The supporting test methods use GB/T 2423.4 alternating damp heat and GB/T 2423.17 neutral salt spray (ISO 9227). The judgment refers to ISO 4628-3, and the corrosion level is not inferior to Ri1. The base of the lighting electrical ready board body is not allowed to have red rust, and the coating is slightly white and the loss of light is acceptable. The door lock, hinge, sealing strip action and sealing function are intact.

The strict B-level national standard is the outdoor shell standard test procedure, which adopts a combination of salt spray and wet heat cycle, divided into two 12 day cycles. A single cycle includes 5 24-hour alternating humid heat cycles and 7 24-hour salt spray cycles; The whole set has a total of 240 hours of wet heat and 336 hours of salt spray, and after continuous testing, there is no red rust on the substrate. There are significant differences in rural environments in Africa, and the minimum requirements of this national standard can be implemented in ordinary humid and hot inland areas; In coastal areas with high salt spray, high temperature and high humidity, project technical specifications are generally stricter. The procurement and acceptance of lighting electrical ready boards often stipulate that there should be no red rust after 240 hours of neutral salt spray and 168 hours of alternating humid heat; The coastal locations with severe corrosion have been further upgraded to a salt spray assessment of 500 hours, suitable for long-term exposure to sunlight, day and night condensation, sand and dust accumulation with salt content.

The experimental conditions are a neutral salt spray 5% sodium chloride solution at a temperature of 35 ± 2 ℃, pH6.5～7.2； Alternating humidity of 40 ℃ and relative humidity of 95%, simulating the fluctuations and condensation of day and night temperature and humidity in Africa. The box is usually made of cold-rolled steel plate+outdoor polyester spray coating, hot-dip galvanized substrate, with a coating thickness controlled at 60 μ m or more, and stainless steel fasteners are used. It needs to be distinguished that the national standard is a sequential combination type test, not simply placed separately; Many suppliers report that producing 96 hours of salt spray alone is only a basic threshold and is not sufficient to meet long-term outdoor operations in Africa. At the end of the experiment, in addition to inspecting the appearance for rust, it is still necessary to verify the insulation, sealing, and opening and closing operations to avoid electrical leakage and water ingress caused by corrosion.