(2)  
Etching Method II (Sodium ammonia)

(a)  
Mix the solution in the container to be used for dipping. The container must be clean and dry, and may be either polyethylene or stainless steel.

(b)  
Place the ammonia bottle on its side or in an inverted position so that liquid ammonia may be drawn off. Fill the dipping container to the level required for the part to be treated. Rubber or Tygon tubing may be used for piping the liquid ammonia.

(c)  
Add metallic sodium chips to the ammonia in a ratio of 10 grams of sodium per liter of ammonia.

(d)  
Stir the solution with a polyethylene or glass rod until all of the sodium is dissolved. The solution will have a dark blue color.

NOTE:  The solution may be deactivated or neutralized by either of the following methods:
1.  
Add a 3-5% solution by volume of water in n-butyl alcohol to the etchant until the etchant is colorless or neutral.

2.  
Allow the ammonia to evaporate. Thoroughly rinse the container with a 3-5% solution by volume of water in n-butyl alcohol. Keep adding rinse solution until no traces of color remain. Finally, rinse with water.

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(e)  
Dip the part to be treated in the solution for 10 to 20 seconds. If the part is not completely covered by the solution, reverse the ends and re-dip for 10 to 20 seconds.

(f)  
If the part does not attain a dark brown color after a 20-second dip, the solution is weak. Add 10 grams of sodium per liter of ammonia to reactivate the solution.

(g)  
Wash the part per steps (1)(c) and (1)(d).

E.  Wipe the etched surface of the teflon pad lightly with clean cloth saturated with MEK.
3.  Repair Teflon Rub Pad

A.  Apply approximately 2 or 3 mils thick film of adhesive to etched surface of teflon pad.
B.  Adhere teflon pad to airplane surface. Press or roll down pad and wipe off excess adhesive along edges.
4.  Restore Airplane to Normal

A.  Allow adhesive to cure for a minimum of 8 hours at room temperature.
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