The complete processing procedure of Dacromet includes pretreatment, coating, low-temperature pre-drying, high-temperature curing & sintering, cooling, post-treatment, inspection and packaging.

Pretreatment is a critical procedure determining coating adhesion and anti-corrosion service life.

(1) Degreasing: Neutral cleaning agents or organic solvents are adopted to remove oil contaminants on workpiece surfaces. Residual grease will seriously impair coating adhesion.

(2) Shot blasting / Sand blasting: Steel shots are sprayed at high speed onto workpieces in an enclosed shot blasting machine to eliminate rust, scale and welding slag, forming proper surface smoothness and roughness. Meanwhile, shot blasting strengthens components and improves fatigue strength.

Additional procedures such as phosphating or multi-alloy diffusion can be added for certain applications, subject to workpiece material and anti-corrosion requirements.

This step evenly applies Dacromet solution onto workpiece surfaces. Three mainstream methods are available:

(1) Dip coating: Immerse workpieces in Dacromet liquid to achieve surface coverage, suitable for mass production of small components.

(2) Spray coating: Spray coating material via spray guns, ideal for large or special-shaped parts.

(3) Brush coating: Used for partial repair or small-batch orders.

For parts with stringent anti-corrosion requirements, double coating & double baking or triple coating & triple baking processes are commonly applied: repeat coating and curing after coating, curing and cooling.

The coating thickness of a single coat (one coating + one baking) is controlled at 6–10μm, and the total final film thickness generally does not exceed 20μm.

Evaporate moisture inside the coating on workpieces to avoid pinholes and blistering caused by direct high-temperature heating, and guarantee coating adhesion.

Film-forming stage: Flaky zinc and aluminum sheets stack together after melting, and chromate undergoes passivation reaction to form a stable inorganic anti-corrosion film.

Insufficient temperature will lead to coating peeling and unqualified salt spray performance; excessive temperature will cause coating chalking.

Cool workpieces to ambient temperature by air cooling. High-strength bolts usually adopt colored sealer topcoat to accurately control the friction coefficient within 0.09~0.22, ensuring stable torque for automatic assembly. The topcoat procedure can be omitted for ordinary chassis brackets.

Carry out tests on film thickness, salt spray resistance, adhesion and appearance. Sort out defective products before packaging and warehousing.