ASTM F2833 Specification covers the basic requirements for chromium-free fastener coatings that combine an inorganic Zinc Rich basecoat with an aluminum-rich topcoat that contains an integrated lubricant. These coatings are applied by conventional dip-spin, dip-drain, or spray methods to ferrous parts which can be handled through a cleaning, or phosphate, coating, and baking operation. Phosphating or shot blast is required to clean and prepare the surface of the steel. These coatings are bake cured at temperatures up to 500°F.
| Grade | Topcoat | Total number of type | Average Coating coating layers Thickness (mil) | Average Coating Weight (g/m3) | Minimum SST hrs |
|---|---|---|---|---|---|
| ASTM F2833 Grade 1 | Organic | 2 | 0.47-0.59 | 32-40 | 840 |
| ASTM F2833 Grade 2 | Organic | 3 | 0.47-0.71 | 32-51 | 1200 |
| ASTM F2833 Grade 3 | Organic/black | 3 | 0.47-0.71 | 37-41 | 840 |
| ASTM F2833 Grade 4 | Inorganic | 2 | 0.47-0.59 | 34-41 | 1000 |
| ASTM F2833 Grade 5 | Organic/various colors | 2 | 0.47-0.59 | 32-39 | 840 |
When the zinc phosphate option is used, its coating weight shall be in the range of 8-20 g/square meter. If used, phosphate to be used in accordance to Specification F1137 grade 0.
These coatings are classified into 5 different types :