TASK 70-23-07-110-023
1 . General.
NOTE:
For nickel-based alloys, TASK 70-23-12-110-027 is the preferred stripping method. You can use TASK 70-23-12-110-027, Stripping Thermal Sprayed Coating, whenever TASK 70-23-07-110-023 is specified in the Engine/Shop Manual.
NOTE:
For stripping thermal spray coatings from titanium parts, do not use this procedure. Use TASK 70-23-12-110-027, Stripping Thermal Sprayed Coating.
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.
NOTE:
TASK 70-23-24-110-001, Ultrasonic Stripping of Rotating Parts, is an acceptable alternative to the process listed in this procedure, provided that the self-substantiation requirements of the TASK are met.
A.When specified in the overhaul manual, this procedure can be used to strip the following thermal spray coatings: Reference sections below.
(1)TASK 70-49-04-340-005, Thermal Spraying Copper-Nickel Alloy (Powder)
(2)TASK 70-49-05-340-006, Thermal Spraying Copper-Nickel-Indium (Powder)
(3)TASK 70-49-02-340-003, Thermal Spraying Aluminum Oxide - Alumina (Powder)
(4)TASK 70-49-33-340-034, Thermal Spraying Aluminum Oxide - Alumina (Powder) - Fine
(5)TASK 70-49-22-340-023, Thermal Spraying Alumina/Nickel-Aluminum Composite (Powder)
(6)TASK 70-49-11-340-012, Thermal Spraying Nickel-Aluminum (Wire)
(7)TASK 70-49-10-340-011, Thermal Spraying Nickel-Aluminum (Powder)
(8)TASK 70-49-14-340-015, Thermal Spraying 75:25 Nickel-Graphite (Powder)
(9)TASK 70-49-15-340-016, Thermal Spraying 85:25 Nickel-Graphite (Powder)
2 . Materials.
Subtask 70-23-07-110-231
A.Refer to TASK 70-00-99-800-001, Solution S0001, or TASK 70-00-99-800-004, Solution S0004.
B.Maskant C10-014  
C.Tape C10-067  
3 . Procedure.
Subtask 70-23-07-110-232
A.Strip coating as directed in the following steps.
CAUTION:
THIS SOLUTION WILL ATTACK MANY ALLOYS IF USED HOT AT 160°F (71°C). DO NOT ELEVATE THE TEMPERATURE WITHOUT PRIOR APPROVAL.
CAUTION:
THIS SOLUTION WILL ATTACK LOW ALLOY STEELS, HASTELLOY B, HASTELLOY W, OR INCOLOY 903. REACTION WITH THESE MATERIALS IS VERY RAPID. BASE MATERIAL MUST BE COMPATIBLE WITH THIS SOLUTION.
CAUTION:
DO NOT USE THIS STRIPPING METHOD ON TITANIUM PARTS. REFER TO TASK 70-23-12-110-027, STRIPPING THERMAL SPRAYED COATING, FOR STRIPPING TITANIUM.
(1)Vapor degrease parts in accordance with TASK 70-21-02-110-002, Cleaning Method No. 2 - Vapor Degreasing, or TASK 70-21-22-110-042, Cleaning Method No. 22 - Light Duty Aqueous Cleaning. Parts must be thoroughly clean to permit uniform stripping.
(2)Mask any metal-sprayed areas that are not to be stripped and resprayed in accordance with the following steps:
NOTE:
Masking is required to protect any metal-sprayed areas that are not to be stripped.
(a)Mask metal-sprayed areas and seal all openings with acid-resistant tape C10-067   or equivalent.
(b)Dip entire parts into Turco No. 537 C10-014   Bubble-free or equivalent, and let dry. Repeat until three coats have been applied.
(c)Trim by cutting through masking tape and maskant around areas to be stripped. Expose only the area to be stripped by peeling away tape and maskant, but do not remove acid-resistant tape/maskant from openings.
WARNING:
STRIPPING SOLUTION IS A STRONG ACID. USE IN A WELL VENTILATED AREA, AND TAKE ALL NECESSARY PRECAUTIONS TO AVOID SKIN- AND EYE-CONTACT. IF SOLUTION CONTACTS SKIN OR EYES, IRRIGATE THOROUGHLY WITH CLEAR WATER AND OBTAIN MEDIAL AID.
(3)Immerse part in stripping solution for the required time. Solution is used full-strength, and stripping rate depends on coating thickness and solution temperature. Heating solution increases stripping rate. Eight hours at 70°F (21°C) to one hour at 110°F (43°C) is recommended.
(4)Remove part from tank. Rinse with a high-pressure water spray. Loosened aluminum oxide and nickel-graphite coatings will spall off exposing blackened bond coat. Remove bond coat by hand, using stiff-bristled brush and running water. Make certain that all traces of coating are completely removed.
WARNING:
ACETONE IS HIGHLY FLAMMABLE. TAKE PRECAUTIONS AGAINST FIRE. AVOID PROLONGED INHALATION OF VAPOR.
(5)Peel maskant and tape from part. Use acetone to remove any maskant that does not peel away readily. Steam clean entire part as directed in TASK 70-21-03-160-001, Cleaning Method No. 3 - Steam Cleaning, then follow with a pure steam "rinse".