company news about 7 Black Surface Treatments for Screws: Ultimate Corrosion Resistance Guide

Meta Description: Discover the pros, cons, and best applications of 7 black screw coatings—from anodizing to Dacromet. Compare costs, durability, and industry uses.

Black surface treatments do more than make screws look professional—they’re critical for corrosion resistance in marine, automotive, and aerospace applications. This guide compares 7 blackening methods with real-world data to help engineers choose the optimal coating.

1. Anodized Black (Best for Aluminum)

• Process: Electrochemical oxide layer (10–25μm)
• Salt Spray Resistance: 1,000+ hours (ASTM B117)
• Cost: $
• Best For: Aircraft components, luxury electronics
• Key Stats:
  • Vickers Hardness: 400–600 HV
  • Thickness Tolerance: ±2μm

Case Study: SpaceX uses Type III anodizing on Falcon 9 aluminum fasteners for salt fog protection.

2. Black Oxide (Cost-Effective for Steel)

• Process: Chemical conversion coating (Fe₃O₄ layer)
• Salt Spray Resistance: 24–72 hours
• Cost: $
• Best For: Automotive brake calipers, tooling
• Limitations: Not for coastal environments

Pro Tip: Pair with oil coating to boost corrosion resistance 3x.

3. Black Zinc Plating (Heavy-Duty Protection)

• Process: Electroplated zinc with chromate passivation
• Salt Spray Resistance: 500–1,000 hours
• Cost: $$
• Industries: Construction, agricultural machinery
• Warning: Banned in EU under REACH for hexavalent chromium

4. E-Coating (Uniform Finish)

• Process: Electrophoretic epoxy/polyester deposition
• Film Thickness: 15–30μm
• Salt Spray Resistance: 800–1,500 hours
• Best For: Automotive underbody screws
• Tesla Example: Model 3 battery pack bolts use black e-coat for HV insulation.

5. Zinc-Nickel Black (Extreme Environments)

• Composition: 85% Zn, 15% Ni alloy coating
• Salt Spray Resistance: 2,000+ hours
• Cost: $$
• Applications: Offshore wind turbines, naval hardware
• NASA Use: Mars rover suspension bolts

6. Black Dacromet (No Chromium Solution)

• Layers: Zn/Al flake + inorganic/organic matrix
• Salt Spray Resistance: 1,000–1,500 hours
• Temperature Resistance: -60°C to 300°C
• EV Adoption: Tesla Cybertruck battery tray screws

7. Black Paint Coating (Budget Option)

• Types: Powder coat (60–80μm), wet spray (25–50μm)
• Salt Spray Resistance: 250–500 hours
• Cost: $
• Ideal For: Indoor furniture, non-critical fixtures

Performance Comparison Chart

Selection Guide: 5 Key Factors

1. Environment:

   • Coastal: Zinc-Nickel or Dacromet
   • High-Temp: Anodizing or Dacromet

2. Budget:

   • Low: Black oxide/paint
   • Unlimited: Zinc-Nickel

3. Conductivity Needs:

   • Non-Conductive: E-coat/paint
   • Conductive: Anodized/Dacromet

4. Aesthetics:

   • Premium Finish: Anodizing/E-coat

5. Regulations:

   • REACH/ROHS: Avoid black zinc (CrVI)

Application Case Studies

• Boeing 787: Zinc-Nickel black screws in wing assemblies
• iPhone 15: Anodized black Pentalobe screws for EMI shielding
• Volvo EX90: Dacromet-coated battery enclosure screws

3 Critical Mistakes to Avoid

1. Mixing Metals: Steel screws with aluminum parts cause galvanic corrosion
2. Ignoring Coating Compatibility: E-coat over zinc requires primer
3. Skipping Pretreatment: Oil residues cause 80% coating failures

FAQs: Expert Answers

Q: Best black coating for saltwater boats?
A: Zinc-Nickel (2,000h) or Dacromet with 316 stainless substrate.

Q: How to repair chipped black coatings?
A: Use touch-up pens with 2K epoxy (e.g., POR-15).

Q: Are black screws conductive?
A: Anodized/Dacromet = conductive; E-coat/paint = insulating.

Why Partner with FINEX?

• ISO 9001-Certified: Batch traceability and full documentation
• Custom Solutions: Black coatings for Inconel®, titanium, exotic alloys
• Fast Turnaround: 72-hour coating services for urgent projects

Free Resource: Download our Coating Selection Checklist