Our factory's requirements for connectors：zinc-plating 8-12μm, color zinc or white zinc, no white rust after 96 hours of salt spray test, no red rust after 200 hours.
ASTM B633 is a standard issued by ASTM International titled:
ASTM B633 – Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel.
1. Scope
This standard applies to electroplated zinc coatings on iron or steel to provide corrosion protection, aesthetic appearance, or a base for paint or other coatings.
2. Types of Coating (based on post-treatment)
Type I: As-plated (no chromate conversion coating)
Type II: Colored chromate (often rainbow or iridescent, known as "yellow zinc")
Type III: Clear or blue chromate (gives a silver/blue appearance)
Type IV: No chromate treatment (bare zinc only)
3. Service Conditions (SC) – based on corrosion resistance level
SC 1: Mild exposure (indoor use or temporary protection)
SC 2: Moderate exposure (storage, non-exposed environments)
SC 3: Severe exposure (industrial, humid environments)
SC 4: Very severe exposure (marine, highly corrosive environments)
4. Recommended Minimum Coating Thickness (depends on service condition)
| Service Condition | Min. Thickness (μm) |
|---|---|
| SC 1 | 5 μm |
| SC 2 | 8 μm |
| SC 3 | 13 μm |
| SC 4 | 25 μm |
If a part is specified as:
"Zinc Plating per ASTM B633 Type II SC 3"
It means:
Zinc electroplated with colored chromate finish
Designed for severe corrosion environments
Coating thickness must be at least 13 μm
