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Aerospace Surface Treatments and Conversion Coatings

GracoRoberts supplies surface treatments and conversion coatings that prepare metal substrates for bonding, painting, and corrosion protection in aerospace OEM manufacturing. Surface preparation is the foundation of every durable bonded or coated joint. The right pretreatment determines whether a structural bond or finish performs across the airframe service life.

Our portfolio covers chromate and chrome-free conversion coatings, corrosion-inhibiting bond primers, and surface etchants, qualified to MIL, AMS, and OEM specifications.

Surface Treatment Types

Chromate Conversion Coatings

Conversion coatings that passivate aluminum and magnesium for corrosion resistance and paint adhesion. Products include Bonderite M-CR 600 AERO (Alodine 600), Bonderite M-CR 1201 AERO (Alodine 1201), and Bonderite M-CR 600RTU.

Chrome-Free Conversion Coatings

Hexavalent-chromium-free pretreatments for programs moving to lower-toxicity finishes. Products include Bonderite M-NT 5700.

Corrosion-Inhibiting Bond Primers

Primers applied to prepared metal before structural bonding to protect the bond line. Products include Solvay BR 127 and BR 127 NC.

Surface Etchants and Preparation

Etchants that prepare fluoropolymer and metal surfaces for bonding. Products include Tetra-Etch fluorocarbon etchant.

Selecting the Right Surface Treatment

The correct pretreatment depends on the substrate, the downstream process, and the controlling specification:
  • Substrate - aluminum, magnesium, titanium, or composite, each with different pretreatment chemistries
  • Downstream process - bonding versus painting, which dictates conversion coating versus bond primer
  • Specification - MIL-DTL-5541 class, AMS, or OEM callout, including chromate versus chrome-free requirements
  •  Application method - immersion, spray, or brush, matched to part size and production setup

Surface treatment is the first step in the bonding workflow. Once surfaces are prepared, see structural bonding systems for compatible adhesives and spec-driven adhesives and sealants for the controlled-material workflow.

Talk to our team about pretreatment selection and qualification for your platform.

Frequently Asked Questions

What is a chromate conversion coating used for in aerospace?

A chromate conversion coating, such as Alodine/Bonderite M-CR, chemically converts an aluminum or magnesium surface into a corrosion-resistant film that also improves paint and adhesive adhesion. It is widely specified to MIL-DTL-5541 for aerospace components.

What is the difference between a conversion coating and a bond primer?

A conversion coating pretreats the bare metal surface for corrosion resistance and adhesion. A corrosion-inhibiting bond primer, such as BR 127, is then applied over prepared metal specifically to protect and stabilize a structural adhesive bond line.

Are chrome-free conversion coatings available?

Yes. Chrome-free pretreatments such as Bonderite M-NT 5700 are available for programs reducing hexavalent chromium. Confirm that the chrome-free option is qualified to your controlling specification before substituting.

Why is Tetra-Etch used before bonding?

Tetra-Etch chemically treats fluoropolymer surfaces such as PTFE, raising surface energy so adhesives and sealants can wet out and bond. It is used where otherwise low-surface-energy materials must be bonded reliably.