TASK 70-23-08-110-024
1 . General.
NOTE:
TASK 70-23-23-330-008, Removal of Coatings by High Pressure Water Stripping, is an acceptable alternative to the process listed in this procedure, provided that the self-substantiation requirements of the TASK are met.
A.This procedure describes the method of stripping pure aluminum and nickel-aluminum thermal spray coatings.
2 . Equipment.
Subtask 70-23-08-110-001
A.The following equipment is required for the application of this process.
(1)Safety equipment and devices which are standard equipment in surface treatment shops such as: eye bath, emergency showers, protective clothing against electroplating products and means for neutralizing acid or alkaline splashing.
(2)Processing plant for neutralizing waste and used solutions.
(3)Efficient ventilation system for extracting and neutralizing vapors.
(4)An alkaline stripping tank made from stainless steel with a heating coil that is capable of heating the solution to 190°F (88°C).
(5)A water rinse tank made from stainless steel (or a carbon steel tank with a polypropylene lining) and a water spray gun, used after the alkaline stripping bath.
3 . Materials.
Subtask 70-23-08-110-002
 
Alkalin Degreasing/Rust Removing Solution - Table 1
 
Solution
No.
Operating Temperature °F (°C)
 
Turco 4181, Turco 4181-L or Turco 4181-GL
S1003
160-180 (71-82)
 
Turco Vitroklene
S1010
160-180 (71-82)
 
Cee-Bee C-46
S1030
160-180 (71-82)
 
Cee-Bee J-84A or Cee-Bee J-84AL
S1139
160-180 (71-82)
 
Ardrox 185 or Ardrox 185L
S1140
160-180 (71-82)
 
MagChem HDL-202
S1151
160-180 (71-82)
 
Eldorado HPT-1150 or 1150L
S1168
160-180 (71-82)
 
Applied 5-840
S1175
160-180 (71-82)
4 . Procedure.
Subtask 70-23-08-110-003
A.Two operations in different solutions are necessary for stripping pure aluminum and nickel-aluminum thermal spray coatings.
(1)Clean part thoroughly by TASK 70-21-03-160-001, Cleaning Method No. 3 - Steam Cleaning. Rinse thoroughly in overflowing water at room temperature. Dip part at least 3 times, letting it drain for a few seconds between immersions.
(2)Strip pure aluminum coating as follows:
WARNING:
STRIPPING SOLUTION IS EXTREMELY CAUSTIC. WEAR PROTECTIVE CLOTHING, GLOVES AND FACE SHIELD TO PREVENT CONTACT WITH SKIN OR EYES. IF SOLUTION CONTACTS SKIN OR EYES, IRRIGATE THOROUGHLY WITH CLEAR WATER AND OBTAIN MEDICAL AID. USE ADEQUATE VENTILATION AND EXHAUST SYSTEM AS HYDROGEN IS LIBERATED DURING STRIPPING.
(a)Slowly immerse part in a tank containing one of the alkaline solutions in table 1, Subtask 70-23-08-110-002, Materials. Keep the part in the solution for 10-15 minutes. If reaction is extremely violent, partially withdraw the part from the solution until the action subsides, then proceed with slow immersion until part is completely covered. Be sure that all areas of part have been immersed for the specified times. Stripping of pure aluminum is normally complete when all visible frothing or bubbling has stopped.
(b)Rinse thoroughly in overflowing water by dipping and draining at least 3 times. Finish by spray-rinsing, being careful to flush all spaces in which stripping solution could be trapped. Repeat 4.A.(2)(a) and 4.A.(2)(b) if necessary.
NOTE:
In some instances a discolored area may be observed after stripping. This discoloration can be removed by rinsing in tap water and brushing with a nylon or fiber brush. (Do not use a wire brush.) If necessary, the part may be returned to the stripping solution for an additional 5 minutes, followed by the rinse operation.
(3)Strip nickel-aluminum bond coat from titanium as directed in TASK 70-23-12-110-027, Stripping Thermal Sprayed Coating, and TASK 70-23-07-110-023, Stripping of Thermal Spray Aluminum Oxide, Non-Ferrous, and Bond Coatings, for other materials.