What are Surface Enhancements?

A surface enhancement is a manufacturing process that adds a layer or additional treatment to the surface of a product or component. Surface enhancements are often considered the “finishing touch” and serve to achieve a desired look or protective layer, depending on the application and service environment of the component. Some metal finishers offer NADCAP certified surface finishing, which adheres to the stringent requirements of NADCAP to ensure consistency and quality.

The aerospace industry relies on a range of metal finishing capabilities to ensure performance and durability in extreme service environments. Common types of aerospace metal finishing include:

Anodizing

Anodizing is a metal finishing process, specifically electrolytic passivation. The metal surface of an aerospace component is coated with a protective oxide layer, which protects against corrosion and wear and extends the lifespan of the part. Anodizing can also serve as a decorative finish or provide electrical insulation.

Different types of anodizing—such as a sodium dichromate seal, nickel acetate seal, or specific spec—provide different benefits, such as improved paint adhesion or better performance in harsh environments. Specific requirements may differ, depending on the relevant aerospace, military, and OEM specifications.

Relevant specs and accreditations include AMS 2471, MIL-PRF-8625, and NADCAP anodizing. 

Conversion Coating

Also referred to as chemfilm coating, conversion coating is an aerospace metal finishing method providing a range of benefits. The process often involves ten or more tanks, each designated for a specific chemical treatment. Conversion coating prepares surfaces for superior bonding and paint adhesion and improves the corrosion resistance and durability of the part. Conversion coating also supports electrical connectivity.

For applications or specs where environmental interactions are a concern, RoHS-compliant conversion coating methods are available.

Relevant specs and accreditations include MIL-DTL-5541, AMS 2473, and NADCAP chemical processing.

Passivation

Unlike anodizing, which leverages electrolysis, passivation is a non-electrolytic metal finishing process. Passivation creates an inert oxide protective barrier on the surface of a stainless steel part, improving corrosion resistance. Passivation also removes any iron that may be left behind by the machining or manufacturing processes, reducing the risk of a corrosive reaction between the two metals.

Two common types of passivation, categorized by NASA, include Type 6 and Type 8. Type 6 uses nitric acid at a lower temperature. Type 8 uses high-concentration nitric acid at a medium temperature.

Relevant specs and accreditations include NADCAP chemical processing.

Shot Peening

Shot peening is a surface enhancement that creates a desired effect via impact. Small media, such as ceramic spheres or conditioned cut wire, are blasted against the surface of a metal component at high velocity. The result is localized plastic deformation and a layer of compressive stress, which protects against cracking and improves fatigue resistance. Some shot peening systems are CNC-controlled, which delivers precise, repeatable results. 

Relevant specs and accreditations include NADCAP shot peening.

The Benefits of Aerospace Metal Finishing Services

Aerospace surface finishing offers considerable benefits for aircraft parts and components.

Performance Improvement

Surface enhancement processes can boost the performance of individual components and, consequently, the aircraft as a whole. Metal finishing can reduce drag and minimize air resistance, which in turn improves the efficiency of the aircraft and supports better fuel economy.

Corrosion Resistance

The protective layers created by anodizing, conversion coating, and other metal finishing applications create a barrier against moisture, salt, chemicals, and other debris in the service environment, improving corrosion resistance. Parts with better corrosion resistance often boast a longer service life, even in harsh conditions, such as wet climates and field environments.

Wear Resistance

Hard coatings and platings improve the durability of aerospace components by making their surfaces harder. These surface enhancements protect against friction and abrasion, so the part doesn’t wear down. This can minimize maintenance delays and even prevent failures caused by worn-out parts.

Fatigue Resistance

Fatigue resistance is a critical attribute for aerospace components that will be subjected to cyclic loading while in service. Shot peening and stress relief baking are excellent metal finishing options for increasing the fatigue strength of aerospace parts.

Boost Aerospace Performance with NAP

Metal and surface finishing can make a significant difference in the performance, durability, and corrosion resistance of critical aerospace components. The right surface finishing method can deliver tremendous results, including improved fatigue resistance, better fuel economy, and more.

National Aerospace Processing (NAP) is a trusted provider of NADCAP certified surface finishing services, including chemical coatings, shot peening, and anodizing, for aerospace components. We have years of experience performing metal finishing services for respected aerospace manufacturers and military branches. Our dedicated surface finishing facilities are NADCAP accredited and optimized for aerospace components, so we can accommodate large parts and a wide range of production volumes. Additionally, NAP is located on American soil, so you can avoid the stresses of tariff fluctuations and the unpredictability of the global supply chain.

To get started on an aerospace metal finishing project, contact us.