Structural Adhesive

EC-1648 B/A

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Product Application

(continued)

Aluminum

1. Vapor Degrease – Hang face sheets in condensing vapors of perchloroethylene for

5 minutes.

2. Alkaline Degrease – Immerse face sheets Oakite No. 164 solution (9-11 oz./gallon

water) at 180-200°F (82-93°C) for 10-20 minutes. Rinse in generous quantities of

clear running water.

3. Acid Etch – Place face sheets in either of the following solutions for 10 minutes at

150 ± 5°F (66 ± 2°C).

A

B

Distilled Water

30 parts by wt.

30 parts by wt.

Sulfuric Acid (Conc.)

10 parts by wt.

10 parts by wt.

Sodium Dichromate

1 part by wt.

4 parts by wt.

4. Rinse – Rinse face sheets in clear running water.

5. Dry – Air dry 15 minutes; force dry 10 minutes with parts at 150 ± 5°F (66 ± 2°C).

6. If primer is used, priming should be done within 4 hours after surface preparation.

Adhesive Mixing

Mix only those amounts of adhesive which can be used within the work life of the

mixture. To achieve optimum physical properties of the adhesive, mixing of the base

and accelerator must be very thorough. Care should be taken not to incorporate

excessive air into the adhesive during the mixing and application as the entrapped air

will tend to give a porous and weakened bond. When weighing the components, be sure

that containers are free of wax or oil. When thoroughly mixed, the adhesive should be

a uniform green color. As a final check to insure that the components are adequately

mixed, spread a thin film on white paper and examine closely for streaks of base or

accelerator. Temperature of the adhesive should not exceed 80°F (27°C) during mixing.

Work Life

After mixing, the mixture remains workable for a time before it becomes too viscous to

properly wet the surface to which it is applied. The work life and rate of cure are both

greatly affected by temperature and to some extent by humidity; curing faster as

temperature and humidity are increased. The work life of a one-pound bath of the

mixture is approximately 90 minutes providing the mixture is maintained at room

temperature (73°F [23°C]) and stirred frequently to minimize localized temperature

increases.

Equipment Suggestions

Application can be made with a spatula, trowel, or flow equipment. Suitable two-part

mixing and metering equipment is available. Contact your 3M representative for

assistance in selecting application equipment to suit your specific needs.

Cure Cycle

In general, the curing of 3M™ Scotch-Weld™ Structural Adhesive EC-1648 B/A

to a thermoset condition is a time-temperature relationship. The only pressure

requirement is that the parts must be held in contact and alignment during the cure cycle.

To effect a useful cure in a reasonable length of time, a minimum temperature of 40°F

(4°C) is required.

The following cure cycle is suggested to obtain dense glue lines which give the

strengths reported in the Test Results section.