Standard for Scratch Resistance of Spray Coating on African Rural Lighting Ready Board Box

Facing the simple transportation, manual handling, and extensive installation conditions in rural Africa, the scratch resistance of the outer surface of the box is sprayed with plastic, with pencil hardness as the core acceptance index, and the execution standards refer to GB/T 6739 and ASTM D3363. Minimum requirement: The hardness of the coated pencil should be ≥ 2H. It should be tested using a standard pencil hardness tester with a 45 ° angle and a 750g load. After repeated scratching, there should be no permanent scratches that penetrate the coating or expose the substrate. Minor shallow scratches are acceptable to prevent large areas of exposed steel rust caused by transportation bumps, rope dragging, and sand and gravel friction.

Supporting hard conditions: The dry film thickness on the outer surface is 60-80 μ m, and the film thickness in the corner weld area is not less than 45 μ m. Insufficient thickness will directly reduce the scratch resistance. The adhesion is tested according to the GB/T 9286 grid method and reaches level 0-1, ensuring that the coating does not peel or peel off under scratching and impact; Impact resistance of 50kg · cm, simulating loading and unloading impacts, with no cracks or peeling of the coating.

Priority should be given to using weather resistant polyester powder for coatings, taking into account outdoor UV aging and surface hardness; Epoxy polyester hybrid type can be used as an alternative, and it is not recommended to use pure epoxy powder for long-term outdoor deployment. The hardness alone is not enough to completely protect the extensive logistics, and the technical specifications should synchronously require that the corners of the box should be equipped with corner guards, and the packaging should be paved with foam for isolation.

If the project requires higher quality and reduced on-site appearance complaints, the index can be increased to 3H wear-resistant modified polyester powder to resist continuous friction from iron and gravel during loading and unloading. All scratch resistance tests must be sampled on fully cured workpieces. Insufficient curing will significantly reduce the hardness of the coating. The factory inspection must keep test records item by item to meet the third-party inspection requirements of African projects.