Fastener Coatings Guide: Zinc to Powder Coating | SC Fastening

Understanding Fastener Coatings: From Zinc to Powder Coating and Beyond

Your complete guide to choosing the right coating for optimal fastener performance

In the industrial world, selecting the right fastener is more than just picking the correct size or thread—it also means choosing the best coating for the job. Fastener coatings play a vital role in enhancing corrosion resistance, improving appearance, and ensuring long-term performance in various environmental conditions. Whether you’re working on construction, automotive, marine, or general manufacturing, the right coating can make all the difference.

Let’s explore the most common and specialized fastener coatings available today.

1. Zinc Plating

Purpose: Zinc is one of the most widely used coatings for fasteners due to its excellent corrosion resistance and cost-effectiveness. Zinc acts as a sacrificial layer, corroding before the steel fastener underneath.

Variants:

  • Clear Zinc (Blue/White): Provides basic corrosion resistance and a clean silver appearance
  • Yellow Zinc (Zinc Dichromate): Offers slightly better corrosion protection than clear zinc, with a gold/yellow appearance
  • Black Zinc: Offers similar properties to clear zinc but with a black finish for aesthetic or camouflage applications

Best For: Indoor applications, light-duty environments, and aesthetic use.

2. Hot-Dip Galvanizing

Purpose: In this process, fasteners are dipped into molten zinc, creating a much thicker protective layer than electroplated zinc. This provides superior corrosion protection.

Advantages:

Note: Galvanized coatings add thickness to the fastener, so they may require oversizing for proper thread engagement.

Best For: Structural steel, outdoor construction, marine, and agriculture.

3. Mechanical Galvanizing

Purpose: Similar to hot-dip galvanizing but applied using a mechanical process at room temperature. It offers consistent coating thickness and avoids hydrogen embrittlement.

Best For: Structural applications where hydrogen embrittlement is a concern.

4. Phosphate Coating

Purpose: Provides mild corrosion resistance and improves paint adhesion. Typically found in automotive or construction applications where fasteners will be painted or coated again.

Types:

  • Zinc Phosphate
  • Manganese Phosphate

Best For: Indoor use, primer coating, or fasteners used in assembly lines.

5. Black Oxide

Purpose: A conversion coating that adds minimal thickness to the fastener. It offers limited corrosion protection unless combined with oil or wax.

Best For: Indoor applications where aesthetics matter, such as electronics, firearms, or decorative metalwork.

6. Powder Coating

Purpose: Powder coating involves applying a dry powder (usually polyester or epoxy) and curing it under heat to form a hard, durable, and colorful finish.

Advantages:

  • Wide variety of colors available
  • Excellent resistance to UV, corrosion, and impact
  • Can be customized to match branding or product design

Best For: Custom projects, architectural applications, and when aesthetics and durability are both priorities.

7. Ceramic Coatings

Purpose: Ceramic-based coatings, like PTFE (e.g., Xylan®), are used when extreme corrosion resistance and low friction are needed.

Advantages:

  • Excellent chemical resistance
  • High-temperature resistance
  • Ideal for marine, chemical processing, and automotive exhaust systems

8. Stainless Steel Coating

Although stainless steel is inherently corrosion-resistant, coatings are sometimes added for extra protection or appearance. Coatings like passivation or black oxide are common for enhancing natural stainless features.

How to Choose the Right Coating

When selecting a fastener coating, consider:

  • Environmental Exposure: Will it be exposed to moisture, chemicals, or salt?
  • Strength Requirements: Coating should not compromise fastener integrity
  • Appearance: Is color or finish important?
  • Budget: Some coatings cost significantly more than others

Partner with SC Fastening Systems

At SC Fastening Systems, we provide a full range of coated fasteners to meet your needs—whether you’re looking for zinc-plated bolts for a light-duty application or powder-coated fasteners for a custom project.

With decades of experience and deep industry knowledge, we’ll help you find the right fastener and coating combination for every job. Explore our coating options or contact our experts today.