Brazing Salt Entrapment
Test Procedure

CMP 0018-B

1. PURPOSE:
1. To establish a procedure for in house testing of entrapped brazing salts or incomplete cleaning of aluminum dip brazed assemblies.
2. MATERIALS REQUIRED - Temperature controlled water bath w/thermometer, distilled water, graduated cylinder, small beaker, 20% solution of silver nitrate (Gilmer Industries), nitric acid, tap water, and an eye dropper
3. BATH PREPARATION
1. Rinse with and fill the water bath with distilled water.
2. Suspend thermometer in the water bath so it touches neither the sides no the bottom.
3. Bring the temperature of the water bath to 170 degrees F and maintain the temperature within the range of 160 to 180 degrees F.
4. Mix 5 ml of 20% silver nitrate solution with 15 ml of distilled water. Then add several drops of nitric acid to acidify the mixture. This makes a 5% solution of silver nitrate.
5. To demonstrate a typical chloride precipitate, (controlled test failure) add 10 drops (using the eye dropper) of the 5% silver nitrate solution to 10 ml of tap water and note the cloudy white precipitate that forms and drops out of solution.
6. Remove a 10-ml water sample from the water bath and add 10 drops of the 5% silver nitrate solution to it. If no precipitate forms, proceed with testing the dip brazed assemblies. If a precipitate forms, discard the water in the water bath, rinse with distilled water, refill with distilled water and repeat the test of the water bath until no precipitate forms (Paragraph 3.1, 3.2, 3.3 and 3.6).
4. TESTING
1. Rinse the parts to be tested in distilled water. Place the parts in the water bath for 15 minutes. Draw from bath a 10-ml sample and add 10 drops of the 5% silver nitrate solution to it. If a white precipitate forms, the parts contain entrapped or not removed salts and will need further flux removal treatment and retesting to this procedure. If no precipitate appears, the parts are accepted.