DESIGN FOR MANUFACTURING (DFM) GUIDE

Designing for Corrosion Resistance

Ensure your product's longevity and performance by choosing the right material and finish. This guide covers the fundamentals of preventing rust and corrosion in metal parts.

What is Corrosion?

Corrosion is the natural process where a refined metal gradually degrades through a chemical or electrochemical reaction with its environment. The most common form of corrosion is rust, which occurs when iron or steel alloys are exposed to oxygen and moisture.

Designing for corrosion resistance involves selecting materials that are inherently resistant to this process or applying a protective surface coating to isolate a vulnerable material from the environment.

A complex part machined from 316L stainless steel, a highly corrosion-resistant alloy

Inherently Corrosion-Resistant Metals

The best way to fight corrosion is to choose a material that doesn't corrode easily in the first place.

Stainless Steel

Thanks to its chromium content, stainless steel forms a passive, self-healing oxide layer. 316L grade offers superior resistance, especially against chlorides, making it ideal for marine and medical use.

Aluminum

Like stainless steel, aluminum naturally forms a protective oxide layer that prevents further corrosion. This makes it lightweight and corrosion-resistant, perfect for outdoor and automotive applications.

Brass & Copper

These copper alloys do not rust but will tarnish or oxidize over time, forming a greenish patina. They offer good resistance in many environments, especially for plumbing and electrical fittings.

Protective Finishes for Vulnerable Metals

For materials like mild steel, a protective barrier is essential to prevent rust.

Anodizing (For Aluminum)

While aluminum is naturally resistant, anodizing significantly enhances this resistance. It's an electrochemical process that creates a much thicker, harder, and more durable ceramic oxide layer on the surface, providing excellent protection and the option for cosmetic coloring.

Powder Coating

This process applies a durable polymer coating to a metal part. It creates a complete physical barrier between the metal and its environment. It's an excellent and cost-effective way to protect steel parts from rust while also providing a decorative finish in a wide range of colors.

Corrosion Resistance FAQ

What is "passivation" for stainless steel?

Passivation is a chemical cleaning process that removes free iron and other contaminants from the surface of stainless steel parts after machining. This process enhances the natural formation of the passive oxide layer, maximizing the material's corrosion resistance.

What is galvanic corrosion?

Galvanic corrosion can occur when two different types of metals are in direct contact in the presence of an electrolyte (like saltwater). The more "noble" metal will cause the more "active" metal to corrode at an accelerated rate. For example, a steel bolt in an aluminum part can cause the aluminum around the bolt to corrode. This is a key consideration when designing assemblies with multiple metals.

Which finish is better for protection: anodizing or powder coating?

Both are excellent, but they work differently. Anodizing is a conversion of the aluminum itself, so it won't chip or peel, but it can be scratched. Powder coating is a distinct layer on top of the part, making it very resistant to scratching and chipping, but a deep scratch that exposes the metal underneath can become a point for corrosion to start.