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What is GMW16721 aluminum pretreatment?

GMW16721 is a General Motors Standard for aluminum pretreatment, or conversion coating, to support structural adhesive bonding.

The standard covers requirements and processes of a pretreatment system for conditioning aluminum substrates to achieve structural adhesive bonds.

GMW16721 pretreatment sets strength and durability requirements for all types of aluminum substrate for use in structural bonding applications in the automotive industry.

GMW16721 Background

Cohesive Separation Mode

An aluminum substrate pretreated to this specification and bonded with an approved structural adhesive will demonstrate cohesive separation within the adhesive layer when stressed to bond delimitation.

Standardized Surface Condition

Requires a review of a surface level of de-ox and etch on a production sample of received substrate. The degree of de-ox and etch depends on the actual thickness of aluminum oxide present on the substrate. Oxide thickness can vary within a narrow bandwidth depending on several factors.

Conversion Coating

An SAF Conversion Coating is a proper corrosion resistant aluminum surface treatment for painting, powder coating, and adhesive bonding. These coatings are applied through an immersion process and are compatible with most aluminum alloys.

Non-chrome coatings are often specified where environmental considerations are paramount. Chrome conversion coatings provide an extra measure of corrosion resistance and can also be used as a standalone finish.

SAF Conversion Coatings can be used to meet:

  • Military specification MIL-DTL-5541, ISO 8081:1985.
  • Tesla Technical Specification (TS- 0002074)
  • Ford Arizona Proving Ground Equivalent (APGE) corrosion test FLTM BI 213-01 at 15 and 30 cycles on specified alloys.
  • General Motors – GMW16721 Aluminum Pre-treatment to Support Structural Adhesive Bonding

SAF contains in-house facilities for lap shear testing and APGE aging of adhesive bonded aluminum. We have developed extensive experience in testing for aluminum adhesive bonding applications in the transportation industry.

Aluminum Pretreatment