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The Duojia Black Oxide Hex Bolt is a high-strength fastener designed for applications in heavy industry, general industry, machinery, and automotive sectors. Manufactured from carbon or alloy steel, these bolts are treated with a black oxide conversion coating. This finish provides a sleek, matte black appearance, minimal corrosion resistance suitable for dry, indoor environments, and does not add any dimensional thickness, making it ideal for parts with tight tolerances. Available in a range of high-strength grades, these bolts are an excellent choice for securing heavy-duty components where aesthetics and precise fit are important.
The product page contains several significant errors and misleading statements. The following points provide an accurate description of this product:
| Paramètre Poste | Description des spécifications |
|---|---|
| Nom du produit | Black Hex Bolt |
| Nom de la marque | Duojia |
| Lieu d'origine | Hebei, Chine |
| Matériau | Carbon Steel / Alloy Steel |
| Grade (Strength) | 4.8, 8.8, 10.9, 12.9 |
| Traitement de surface | Black Oxide Coating |
| Gamme de tailles | M6 to M24 |
| Système de mesure | Métrique |
| Application | Heavy Industry, General Industry, Machinery (Indoor Use) |
| Certifications | ISO9001, ISO14001, ISO45001, SGS |
| Options d'emballage | Petit paquet+carton+palette ; sac/boîte avec palette |
Black oxide is a chemical process that creates a magnetite (Fe₃O₄) conversion coating on the surface of the steel.



