How to Choose the Best Plating for Your Metal Seals: A Complete Guide

Metal seals need the right plating to handle harsh environments, resist corrosion, and ensure performance. Here's what to focus on when choosing plating:

• Environment: Consider temperature extremes (–270°C to 650°C), pressure (up to 500 MPa), and chemical exposure.
• Durability: Choose plating that minimizes wear and friction.
• Conductivity: Materials like silver (high conductivity) or gold (corrosion-resistant) suit specific needs.
• Industry Standards: Ensure compliance with MIL-STD, ASTM, or other regulations.

Quick Comparison

Start by understanding your operating conditions, define performance needs, and ensure compliance with standards. This helps extend seal life and reduce downtime.

Sonkit's Metal Seal Design Guide

Plating Selection Criteria

Choosing the right plating is key to improving both durability and performance in various applications.

Operating Environment

Materials in industrial settings often face extreme conditions. These can range from incredibly low temperatures of –270°C to high temperatures of 650°C (1,202°F). Additionally, seals are frequently exposed to harsh chemicals, requiring plating that can handle corrosive substances. For instance, in semiconductor manufacturing, seals must tolerate specialized cleaning agents while maintaining proper surface conditions.

Physical stresses, such as pressure and friction, also play a major role in determining the appropriate plating.

Physical Requirements

Plating must be durable enough to handle wear and control friction effectively. In high-pressure scenarios - reaching up to 500 MPa (72,500 psi) ^[1] - plating materials need to maintain their integrity. The right choice minimizes wear on moving parts and ensures seals perform consistently under fluctuating pressures.

Conductivity Needs

Thermal conductivity is another critical factor when selecting plating materials. Here's how common options compare:

Silver is the best for conductivity but tarnishes easily ^[3]. Gold, while slightly less conductive, offers excellent corrosion resistance, making it ideal for applications where reliability is crucial ^[2].

Industry Standards

"Metal selection should consider working conditions such as temperature and pressure, and factors such as corrosion resistance and chemical compatibility must be met" ^[1].

Plating choices must align with certifications and regulations, such as:

• MIL-STD
• ASTM International
• Specific industry requirements
• Environmental regulations

Balancing these standards with practical factors like cost and material availability is essential for effective plating selection.

Common Plating Materials

Selecting the right plating material depends on its specific properties and how well it performs in different conditions. Below is a breakdown of commonly used plating materials, their features, and typical applications.

Gold Plating Properties

Gold plating is known for its strong resistance to corrosion and excellent electrical conductivity. Here's how these properties benefit metal seals:

Silver Plating Uses

Silver plating combines excellent conductivity with a smooth finish, making it ideal for controlled, dry environments.

Nickel Plating Applications

Nickel plating is valued for its durability and resistance to wear. The electroless nickel process ensures even coating and shields components from corrosive agents like salt water, carbon dioxide, oxygen, and hydrogen sulfide.

Alternative Plating Types

Electroless plating is particularly effective for coating complex shapes evenly while offering strong corrosion resistance.

Understanding these materials is crucial for choosing the best option for specific industrial needs.

Industry-Specific Plating Guide

Different industries require plating solutions tailored to their specific challenges. Here's a breakdown of material choices designed to perform under extreme conditions.

Aerospace Plating

Aerospace seals are exposed to extreme temperatures and tough environments. Titanium plating is a top choice here due to its lightweight strength and ability to withstand high temperatures.

Oil and Gas Plating

In oil and gas, seals need to endure both corrosion and intense pressure. For subsea equipment or other high-pressure systems, select plating that resists harsh chemicals and withstands these demanding conditions.

Semiconductor Plating

Semiconductor applications call for ultra-precise and clean plating. For areas with high contact pressure, hard gold is the go-to. Silver, on the other hand, offers a budget-friendly option for conductivity in controlled settings. Key details include:

• Gold plating thickness: 0.25–2.5 microns per side
• Underplate: Copper or nickel for better adhesion and as a diffusion barrier
• Surface finish: Hard gold alloyed with nickel or cobalt to handle high contact pressure

Here's a quick comparison of common plating types in semiconductor use:

Plating Performance Tips

To get the best results from your plating process, it's essential to focus on both material selection and application techniques. Here's how to fine-tune your plating performance.

Surface Prep Methods

The foundation of effective plating lies in proper surface preparation. A clean and well-prepped surface ensures strong adhesion and reduces the risk of issues like delamination. Start by cleaning the surface thoroughly. For intricate shapes, ultrasonic systems are great for removing oils, grease, and tiny contaminants. If you're working with delicate parts, laser cleaning is a precise option that avoids damaging the material.

You'll also need to create the right surface profile by roughening it carefully. Choose a method based on your specific needs:

Once the surface is ready, accurate measurement is the next step.

Plating Measurements

After prepping the surface, measuring plating thickness accurately ensures quality and compliance. Use these steps:

1. Mark key points on technical drawings and record thickness readings to align with ASTM, MIL, or AMS standards.
2. Follow all relevant industry guidelines.
3. Document the results to confirm that the average thickness falls within the 75 µin tolerance range.

"Significant surfaces" are typically defined as any area that a 0.75-inch diameter sphere can touch.

Inspection Guidelines

Routine inspections are essential for maintaining plating quality over time. Key practices include:

• Using real-time surface analysis to check conditions before and after plating
• Performing adhesion tests on sample pieces from every batch
• Looking for visual issues like discoloration or uneven coating
• Keeping track of environmental factors during storage and handling

For critical applications, advanced analysis methods can confirm coating integrity and catch potential problems early, ensuring reliable performance.

Summary

This guide has covered the main criteria and material options to help you choose the right plating for your industrial needs. The performance and lifespan of metal seals largely depend on factors like temperature, pressure, and chemical exposure in your operating environment.

Here's a quick recap of the key factors:

These factors are essential to selecting the right plating, ensuring better seal performance and minimizing downtime.

What to keep in mind:

• Understand your operating conditions
• Define your performance expectations
• Ensure compliance with industry standards