MIL-STD-419E
5.3 Pickling and hydrostatic tests (prior to installation). Pickling and hydrostatic tests shall be in accordance with the procedures specified herein. Caution shall be exercised by the operator during the pickling process insofar as time of immersion in the acid bath is concerned. The assembly shall remain in the bath only long enough to permit adequate pickling (removal of scale), as determined visually. Due to the nature of the pickling process, this caution is necessary to ensure and protect the mechanical properties of the pipe, tubing, or fitting. The position of the tubing in the pickling bath shall be changed occasionally to make sure that if gas pockets form they shall not
always be at the same location. When hydraulic fluid is used for hydrostatic testing, the assembly shall be degreased just prior to further brazing or welding.
5.3.1 Nonferrous pipe, tubing, and fittings (bronze, copper, copper-nickel, and nickel-copper, not aluminum or aluminum alloys). Aluminum and aluminum alloys shall not be pickled.
5.3.1.1 Nonferrous metals other than nickel-copper. The pickling procedure shall be as follows:
a. Pickle free from scale in a solution of the following composition at 60 to 100 °F:
(1) Sulfuric acid, 66 degrees Baume, specific gravity (sp. gr.), 1.83, conforming to Type I, Class 1 of
A-A-55828 - 7 to 14 fluid ounces. (2) Water - 1 gallon.
(Caution: The acid shall always be added carefully with stirring to cooled water. This mixing procedure shall always be followed when adding concentrated sulfuric acid to water.)
Note: If red stains appear, immerse the work briefly in a solution formulated as above but which contains, in addition, 2 to 4 ounces of sodium dichromate (per gallon of water) conforming to A-A-59123. This solution shall be maintained at a temperature range of 70 to 120 °F.
5.3.1.2 Nickel-copper. The pickling procedure shall be as follows:
a. Pickle for 20 to 40 minutes in a hot solution (180±10 °F) of the following composition:
(1) Hydrochloric acid, 20 degrees Baume, sp. gr 1.16 (in accordance with ASTM E1146) - ½ gallon. (2) Cupric chloride - 4 ounces.
(3) Water - 1 gallon.
b. Rinse in warm water (over 120 °F).
c. Immerse for 5 to 10 minutes in a bath composed as follows (temperature 70 to 100 °F).
(1) Sulfuric acid, 66 degrees Baume, sp. gr. 1.83 conforming to Type I, Class 1 of A-A-55828 - 13 fluid
ounces.
(2) Sodium dichromate (in accordance with A-A-59123) - 17½ ounces
(3) Water - 1 gallon.
5.3.1.3 Treatment following pickling. The treatment following pickling shall be as follows:
a. Immediately after pickling, rinse in a clean, warm water bath.
b. Neutralize traces of acid from the pickling operation by rinsing the work in an alkaline bath containing 4 ounces (per gallon of water) of sodium carbonate in accordance with A-A-59563.
c. Rinse thoroughly in fresh, warm water (over 120 °F).
d. If hydrostatic test will not be performed with water (see 5.3.1.4), dry with clean air.
5.3.1.4 Hydrostatic test prior to installation. The piping assembly shall be subjected to the specified test pressure (usually specified in system diagrams) with tap water or with hydraulic fluid equal to, or compatible with, which is normally used in the system. If leaks occur, they shall be repaired and the assembly retested. Following a satisfactory test, the solution shall be drained and all openings capped. If water is used, the assembly shall be blown dry by clean dry air before openings are capped. The piping assembly shall then be installed up to the components (see 4.2).
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