Dacromet VS Mechanical Galvanizing, Anti‑corrosion Solution Selection For High‑Strength Fasteners

For alloy‑steel fasteners above grade 8.8, conventional electro‑galvanizing brings hydrogen‑embrittlement fracture risk. Dacromet and mechanical galvanizing are two mainstream hydrogen‑free anti‑corrosion solutions, widely applied in construction machinery, wind power and rail transit components.

Dacromet, also known as zinc‑flake coating, forms protective film by cross‑linked zinc‑aluminum flakes. Coating thickness ranges 5‑12μm, neutral salt‑spray resistance reaches 500‑1000 hours. Thin coating keeps thread dimension stable for smooth assembly. It performs well under high temperature up to 250°C, while its cost is relatively high.

Mechanical galvanizing uses impact medium inside rotating barrel to cold‑weld zinc powder onto parts. Without electrolysis or acid pickling, hydrogen embrittlement is avoided. Coating thickness is adjustable. Its salt‑spray performance sits between electro‑galvanizing and Dacromet. It has dark‑grey granular appearance and slight thread build‑up, with better cost performance for large‑volume orders.

Selection guide: Choose Dacromet for long salt‑spray requirement, precise thread matching and high‑temperature working conditions. Mechanical galvanizing is recommended for budget‑sensitive outdoor projects with high‑strength bolts. For coastal heavy salt‑spray environment, thicker coating or top‑sealer shall be considered for both treatments.

Notes: Neither of them can replace stainless steel. Workpieces must be fully cleaned of oil and rust to prevent coating peeling. Require salt‑spray test reports from suppliers for verification during procurement.