Structural Adhesive Film

AF 32

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Product Application

Proper adhesive application is as important as proper bond design and adhesive choice to obtain maximum joint

properties. Improper adhesive application techniques can result in partial or complete failure of an assembly.

Scotch-Weld AF 32 performance data reported in this data sheet was developed using the following suggested

procedures. Variations from these procedures should be fully evaluated to insure bond properties sufficient to

meet the requirements of your particular application.

Surface Preparations

A thoroughly cleaned, dry, grease free surface is essential for maximum performance. Cleaning methods which will

produce a break-free water film on metal surfaces are generally satisfactory. Surface preparations should be fully

evaluated with the adhesive, especially if resistance to specific environments are anticipated.

Suggested Cleaning Procedure for Aluminum

1. Alkaline Degrease – Oakite 164 solution (9-11 oz/gallon water) at 190°F ± 10°F (88°C ± 5.6°C) for 10-20

minutes. Rinse immediately in large quantities of cold running water.

2. Optimized FPL Etch Solution (1 liter):

Material

Amount

Distilled Water

700 ml plus balance of liter (see below)

Sodium Dichromate

28 to 67.3 grams

Sulfuric Acid

287.9 to 310.0 grams

Aluminum Chips

1.5 grams/liter of mixed solution

To prepare 1 liter of this solution, dissolve sodium dichromate in 700 ml of distilled water. Add sulfuric acid

and mix well. Add additional distilled water to fill to 1 liter. Heat mixed solution to 66 to 71°C (150 to 160°F).

Dissolve 1.5 grams of 2024 bare aluminum chips per liter of mixed solution. Gentle agitation will help

aluminum dissolve in about 24 hours.

To FPL etch panels, place them in the above solution at 150 to 160°F (66 to 71°C) for 12 to 15 minutes.

3. Rinse – Rinse panels in clear running water.

4. Dry – Air dry 15 minutes

Force dry 10 minutes (minimum) at 140°F (60°C) maximum.

5. It is advisable to coat the freshly cleaned surfaces with primer within 4 hours after surface preparation.

Note: Read and follow safety and handling recommendations provided by the suppliers of these materials prior to

preparing this solution.

Primer Application

Advantages

Priming of bonding surfaces offer two distinct advantages: (1) Priming insures complete wetting of metal surfaces

which normally results in superior environmental and low temperature properties, and (2) Priming simplifies

production by protecting cleaned parts until bonding can be completed. 3M™ Scotch-Weld™ Structural Adhesive

Primer EC-1660 has been applied successfully by flow coating, brushing and spraying.

Caution: 3M™ Scotch-Weld™ Structural Adhesive Primer EC-1660 is flammable. See the Scotch-Weld EC-1660

Technical Data Sheet for additional information.

Primer Dry

A primer dry which will result in a solvent free coating is generally satisfactory. Drying temperatures above 300°F

(149°C) should be avoided, since a primer overcure will hinder the wetting action of the adhesive film to the primer.

Suggested Scotch-Weld EC-1660 Dry Cycle:

Air Dry

30 minutes at 75°F ± 5°C (24°C ± 2.8°C).

Force Dry Circulating air oven with part above 200°F (93°C) but not exceeding 250°F (121°C) for 30 minutes.

Film Application

1. Cut portion of film to be used from roll with protective liner in place.

2. Place film on substrate using the liner as a protective cover.