ASTM D3933-98 (2025) PDF

Full title and description

Standard Guide for Preparation of Aluminum Surfaces for Structural Adhesives Bonding (Phosphoric Acid Anodizing). This guide describes recommended procedures and requirements for phosphoric acid anodizing of aluminum and its alloys to optimize surfaces for durable structural adhesive bonds.

Abstract

This reapproved guide (original designation D3933-98) provides a concise, practice‑based method for preparing aluminum substrates by phosphoric acid anodizing prior to adhesive bonding. It covers process intent, key preparation steps, and considerations for qualification and quality control so that reproducible, durable adhesive joints can be achieved in structural applications.

General information

• Status: Active / Current (reapproved 2025).
• Publication date: Reapproved 2025 (document activity last updated Feb 27, 2025; originally adopted 1998).
• Publisher: ASTM International.
• ICS / categories: 83.180 (Adhesives).
• Edition / version: D3933-98R25 (reapproved 2025).
• Number of pages: 5 (concise guide).

Scope

This guide describes the requirements for phosphoric acid anodizing of aluminum and its alloys for structural adhesive bonding. It is based on commercial practice and is intended to be used where the surface preparation for qualification and quality‑control testing of adhesives is agreed upon between manufacturer and user. Safety and environmental precautions are noted but the user is responsible for compliance with applicable regulations.

Key topics and requirements

• Purpose and significance of phosphoric acid anodizing to improve adhesive wetting and bond durability.
• Recommended sequence of surface cleaning, etching (as applicable), anodizing parameters and sealing considerations for aluminum alloys.
• Process control and reproducibility: bath composition, time/temperature, and post‑anodize handling to achieve repeatable surfaces.
• Requirements for agreement between manufacturer and user on the specific surface preparation used for qualification and testing.
• Notes on units (SI primary) and responsibility for safety, health and environmental practices.

Typical use and users

Used primarily by engineers and technicians in aerospace, transportation (including automotive), marine, and other industries where structural adhesive bonding to aluminum is critical. Typical users include adhesive manufacturers, materials engineers, surface treatment shops, and test laboratories performing bond qualification and quality control.

Related standards

This guide is part of the ASTM D14 (adhesives) family and is commonly referenced alongside other surface‑preparation and adhesive test guides (for example, Guide D2651 for metal surface preparation and various adhesive test methods). Some collections list cross‑references including D2651, D3165, D4541, D6465 and D7234 as related or referencing documents. Users should consult committee D14 listings for exact cross‑references.

Keywords

aluminum, phosphoric acid anodizing, anodize, surface preparation, adhesive bonding, structural adhesives, substrate preparation, D3933.

FAQ

Q: What is this standard?

A: ASTM D3933-98 (reapproved 2025) is a guide that describes phosphoric acid anodizing methods and requirements for preparing aluminum surfaces intended for structural adhesive bonding.

Q: What does it cover?

A: It covers the scope, purpose, and recommended practices for phosphoric acid anodizing of aluminum and its alloys to produce surfaces suitable for reproducible, durable adhesive bonds; it also notes the need for manufacturer‑user agreement on preparation used for qualification and QC.

Q: Who typically uses it?

A: Materials and bonding engineers, surface treatment suppliers, adhesive manufacturers, and test labs in industries requiring structural adhesive joints (notably aerospace, transportation and similar sectors).

Q: Is it current or superseded?

A: The document is active and was reapproved in 2025 (D3933-98R25). It is a reapproval of the 1998 designation; users should verify currentness for procurement or regulatory purposes.

Q: Is it part of a series?

A: Yes — it is part of the ASTM D14 family of adhesives and surface preparation guidance (subcommittee D14.80). It is often used with other D14 guides and test methods for adhesive qualification and surface preparation.

Q: What are the key keywords?

A: Aluminum, phosphoric acid anodizing, anodize, surface preparation, structural adhesive bonding, adhesive qualification, D3933.