TASK 70-22-02-110-014
1 . General.
CAUTION:
THIS PROCEDURE CANNOT BE USED AS A ROUTINE CLEANING PROCESS BECAUSE IT REMOVES TOO MUCH BASE MATERIAL. THIS PROCEDURE USES AN ALKALINE SCALE CONDITIONER FOLLOWED BY AN ACID ETCH TO REMOVE SCALE AND OXIDE LAYERS (ALPHA CASE). THIS PROCEDURE CAN ONLY BE USED FOR DESCALING AND ETCHING OF TITANIUM WHEN IT IS SPECIFICALLY PERMITTED IN THE PROCESS DOCUMENT.
CAUTION:
THE ALKALINE PERMANGANATE STEP ASSOCIATED WITH THIS CLEANING PROCESS REQUIRES MASKING OF THERMAL SPRAY WEAR COATINGS INCLUDING T400, T800, TUNGSTEN CARBIDE/COBALT AND CHROME CARBIDE/NICKEL CHROME. UNDER CERTAIN CONDITIONS, ALKALINE PERMANGANATES USED IN THIS PROCESS CAN ATTACK SOME THERMAL SPRAY WEAR COATINGS. ALKALINE PERMANGANATES DO NOT ATTACK SEAL TEETH CLEARANCE CONTROL COATINGS OF NICKEL ALUMINUM BOND COAT AND ALUMINUM OXIDE TOP COAT.
NOTE:
If the thermal spray wear coat will be stripped and replaced before the part is returned to service, then the masking is not required.
NOTE:
Thermal spray coatings have a dull gray color while chrome plating has a shiny and lighter color. If FPI is used, a thermal spray coated bearing journal will have an even background glow, while a chrome plate will have the characteristic network cracking pattern.
A.Titanium requires special care in processing to avoid contamination by oxygen or halogen-containing (fluorine, chlorine, bromine, iodine) agents. For that reason, titanium cleaning should be done in an area that is isolated from that area in which TASK 70-21-02-110-002, Cleaning Method No. 2 - Vapor Degreasing, or other parts-cleaning operations are performed. Initial cleaning should be done in accordance with TASK 70-21-03-160-001, Cleaning Method No. 3 - Steam Cleaning. If scale, oxide coating, or other stubborn surface coatings remain after steam cleaning, shell-blasting per TASK 70-21-04-120-B01, Dry Abrasive Blast Cleaning - Method No. 4B, may be used.
2 . Equipment.
Subtask 70-22-02-110-141
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)The alkaline degreasing station shall consist of a stainless steel tank with a heating coil capable of heating the solution to 200°F (93°C).
(5)A water rinse tank made from stainless steel with a polypropylene lining used after alkaline degreasing bath.
(6)The decarbonizing station shall consist of a stainless steel tank with a heating coil capable of heating the solution to 280°F (138°C). An automatic leveling device for water make-up must be included. Tanks constructed of mild steel are suitable but the heating coil or exchangers should be fabricated from a stabilized stainless steel.
(7)A hot water rinse tank made from stainless steel with a heating coil in tank capable of heating water to 140°F (60°C) and an air/hot water spray gun, used after decarbonizing bath.
(8)A water rinse tank made from stainless steel with a polypropylene lining used after hot water rinse.
(9)The acid stripping station shall consist of a stainless steel tank with a polypropylene lining.
(10)A water rinse tank made from stainless steel with polypropylene lining used after the acid stripping bath.
3 . Materials.
Subtask 70-22-02-110-142
 
Consumables - Table 1
 
Consumable
No.
Operating Temperature °F (°C)
 
Turco 524 Maskant
C03-052  
Ambient
 
Turco 625 Demask
C03-053  
Ambient
 
Alkaline Degreasing Solution for Titanium - Table 2
 
Solution
No.
Operating Temperature °F (°C)
 
Turco 4181, Turco 4181-L or Turco 4181-GL
S1003
180-190 (82-88)
 
Turco Vitro-Klene
S1010
160-180 (71-82)
 
Cee-Bee C-46
S1030
180-190 (82-88)
 
Cee-Bee J-84A or Cee-Bee J-84AL
S1139
180-190 (82-88)
 
Ardrox 185 or Ardrox 185L
S1140
180-190 (82-88)
 
MagChem HDL-202
S1151
180-190 (82-88)
 
Eldorado HTP-1150 or 1150L
S1168
180-190 (82-88)
 
Applied 5-840
S1175
180-190 (82-88)
 
Oxide Conditioning Solution for Titanium - Table 3
 
Solution
No.
Operating Temperature °F (°C)
 
Turco 4338 or Turco 4338-L or Turco 4338-C
S1012
160-200 (71-93)
 
Ardrox 188 or Ardrox 188RFU
S1001
160-200 (71-93)
 
Ardrox 1435
S1205
160-200 (71-93)
 
Alkaline permanganate
S1004
160-200 (71-93)
 
MagChem HDP-2524
S1018
160-200 (71-93)
 
MagChem HDL-2524
S1203
160-200 (71-93)
 
Cee-Bee J-88, Cee-Bee J-88A, or Cee-Bee J-88L
S1014
160-200 (71-93)
 
Eldorado HTP 1190
S1163
160-200 (71-93)
 
Eldorado HTP 1190L
S1164
160-200 (71-93)
 
Applied 5-770
S1177
180-200 (82-93)
 
NOTE:
Operating the alkaline permanganate solution in the low end of the temperature range will extend the bath life but may decrease effectiveness. Conversely, operating the batch at the high end of the temperature range will improve cleaning ability at the risk of decreasing bath life and increasing the frequency of de-sludging.
 
Acid Stripping Solution for Titanium - Table 4
 
Solution
No.
Operating Temperature °F (°C)
 
Turco 4104 + HNO3
S1013
Ambient
 
Ardrox 1635 + HNO3
S1029
Ambient
 
Ammonium bifluoride + HNO3
S1191
Ambient
 
Cee-Bee P-109B + HNO3
S1192
Ambient
4 . Special Instructions.
Subtask 70-22-02-110-143
A.Handle titanium parts that will be subjected to temperatures of 1000°F (538°C) or more after cleaning, with clean, lint-free, white cotton gloves, and protect the part with polyethylene wrapping or bag.
B.Do not permit adhesive paper or tapes containing chlorine compounds to come in direct contact with titanium parts.
C.To prevent possible attack of the hardware, ensure that any temporary markers used on titanium hardware meet the requirements of TASK 70-16-02-350-017, Temporary Marking.
D.Critical dimension parts may not be processed for more than five minutes through solutions in table 4 of Subtask 70-22-02-110-142, Material. For longer times, masking must be used.
WARNING:
ACETONE AND METHYL-ETHYL-KETONE ARE TOXIC AND EXTREMELY FLAMMABLE. AVOID PROLONGED BREATHING OF VAPORS AND CONTACT WITH THE SKIN, AND KEEP AWAY FROM SPARKS OR FLAME.
E.When the local water supply contains natural or added chlorine, fluorine, bromine, or iodine, (or their compounds) in excess of 100 ppm, immersion rinsing can be done in tap water if (1) the subsequent operation is done without delay, or (2) the part is immediately pressure-rinsed with distilled or deionized water and blown dry with filtered shop air, or thoroughly wiped dry with clean, lint-free cloth moistened with acetone or methyl-ethyl-ketone.
F.Filler wire, as well as parts to be weld repaired must be cleaned by the acid pickling process. Refer to Subtask 70-22-02-110-144, Procedure. Cleaned wire can be stored in polyethylene bags with desiccant up to 48 hours.
G.When directed by the repair procedure for a given part, mask specified areas as follows before acid pickling.
(1)Dip or brush one coat of Turco 524 Maskant C03-052   or equivalent, on all surfaces to be masked. Masking coat should extend approximately 0.25 inch (6.4 mm) beyond the surfaces to be protected to ensure a good seal. Let the coat dry for about 20 minutes, or until it is dry to the touch. Apply a second coat of masking material, and let dry for 2-3 hours before continuing with acid pickle. Refer to Subtask 70-22-02-110-144, Procedure.
WARNING:
IF REMOVING MASKING BY HAND, WEAR RUBBER OR NEOPRENE GLOVES TO PROTECT SKIN FROM ACID WHICH COULD HAVE GOTTEN UNDER THE MASKING.
WARNING:
NEVER ADD WATER TO ACIDS. ADD ACIDS TO WATER WHILE STIRRING VIGOROUSLY. LOCALIZED HEAT OF SOLUTION CAN CAUSE BOILING AND SPATTERING. WEAR FACE MASK OR TIGHT-FITTING GOGGLES, AND RUBBER OR NEOPRENE GLOVES. IN CASE OF ACCIDENT, FLUSH EYES OR SKIN WITH COOL WATER, AND SEEK IMMEDIATE MEDICAL AID.
(2)Remove masking compound after the rinse following acid pickling either by peeling it off by hand, or by dipping or brushing masked area with Turco Demask 625 C03-053   or equivalent.
5 . Procedure.
Subtask 70-22-02-110-144
A.Clean using a solvent as indicated in the Engine/Shop Manual.
WARNING:
ALKALINE SOLUTIONS ARE VERY ACTIVE AND CAUSE SERIOUS BURNS. AVOID CONTACT WITH SKIN, EYES, AND CLOTHING. IF CONTACT OCCURS, WASH IMMEDIATELY WITH ABUNDANT QUANTITY OF WATER. AVOID BREATHING OF VAPORS.
WARNING:
OPERATOR SHOULD WEAR FACE SHIELD, GLOVES, PROTECTIVE CLOTHING, AND PROTECTIVE SHOES.
B.Immerse the part in a tank containing one of the alkaline degreasing solutions listed in table 2 of Subtask 70-22-02-110-142, Materials. Maintain the solutions at the specified temperature.
Duration: 10 to 15 minutes.
C.Rinse by immersion in water at room temperature.
D.Immerse the part in a tank containing the oxide conditioning solution and maintain at the specified temperature. The oxide conditioning solutions are listed in table 3 of Subtask 70-22-02-110-142, Materials.
Duration: 30 to 60 minutes.
E.Rinse by immersion in hot water at minimum 150°F (66°C) and pressure spray. Rinse over tank while withdrawing the part.
F.Rinse by immersion in water to cool the part.
NOTE:
The part must be thoroughly cooled before immersing it in the next solution.
WARNING:
SOLUTION IS A STRONG ACID. ACID/FLUORIDE SOLUTIONS ARE VERY HAZARDOUS. USE IN A WELL VENTILATED AREA, TAKE ALL NECESSARY PRECAUTIONS TO AVOID SKIN AND EYE CONTACT. IF SOLUTION CONTACTS SKIN OR EYES, WASH IMMEDIATELY WITH LARGE AMOUNTS OF CLEAR WATER AND OBTAIN MEDICAL ATTENTION IMMEDIATELY.
WARNING:
OPERATOR SHOULD WEAR FACE SHIELD, GLOVES, PROTECTIVE CLOTHING, AND PROTECTIVE SHOES.
CAUTION:
USE COATED BASKETS AND OTHER HANDLING DEVICES SO A GALVANIC CELL IS NOT CREATED WHICH COULD DO DAMAGE TO THE PARTS.
G.Lower the part into a tank of one of the acid stripping solutions in Table 4. Take precautions to prevent a galvanic cell (electrolytic coupling) with associated handling devices. Use baskets and other handling devices coated with Teflon or other non-conductive material to give the necessary protection to parts.
Duration: 5 to 20 minutes.
NOTE:
Steps 5.B. thru 5.F. can be repeated again provided that the total time in the alkaline degreasing solution does not exceed 20 minutes and the total time in the oxide conditioning does not exceed 60 minutes. Step 5.G. can be repeated for a total time of 20 minutes.
H.Rinse by immersion in water at room temperature.
I.Rinse by immersion and by spraying with hot water at minimum 150°F (66°C). If the titanium engine part will go directly from this cleaning operation to a thermal repair process (such as welding, brazing, or heat treatment) the final rinse water shall contain less than 50 ppm chloride (as defined in TASK 70-00-05-800-006, Water Types). Any of the steps that follow will meet this requirement:
(1)An overflowing tank of potable water that is always below 50 ppm chloride (as defined in TASK 70-00-05-800-006, Water Types) provided that there is an adequate overflow rate and data to substantiate that the immersion time of the part in the tank is long enough for the dilution of any potential chemical drag in to below the 50 ppm chloride limit.
(2)A final spray rinse with distilled or deionized water.
(3)A stagnant tank of deionized water (either for immersion or spray washer rinsing) that is maintained below 50 ppm chloride (as defined in TASK 70-00-05-800-006, Water Types).
NOTE:
Conductivity probes are frequently used to maintain these tanks within control limits and the parts shall remain in the rinse water until the tank resistivity returns to at least 10,000 ohm-cm (100 Microsiemens/cm).
NOTE:
If the part is going directly to FPI, an oven dry at 150 to 200°F (66 to 93°C) or a hot water (minimum 150°F (66°C)) flash dry is required here. Keep the part submerged until the part reaches a temperature sufficient to provide for flash drying. The final rinse after cleaning (at the end of the FPI process) prior to further processing should be a deionized water rinse, as listed in Steps 5.I.(1), (2), or (3).
NOTE:
The time required will vary with part size, water temperature and tank size. Proper flash drying is indicated by seeing the water on the surface of a part start to "flash" or "whisk" off as the part is being removed from the hot water tank.
J.Use repositioning, suction, blotting with a clean, absorbent material, or by blowing off with an oil and water filtered shop air gun to remove excess water.
K.Dry using clean, dry air.
6 . Quality Assurance.
Subtask 70-22-02-110-145
A.Visually check the part for complete removal of oil and dirt.
B.Make sure that the part is completely dry and that all oxide traces have been removed. If traces of oxide remain after treatment, repeat the procedure and, if required, finish by TASK 70-21-04-120-D01, Dry Abrasive Blast Cleaning - Method No. 4D.
C.Chloride analysis of the rinse water shall be performed in accordance with Step 3 (Definitions and Test Protocol) in TASK 70-00-05-800-006, Water Types.
D.After cleaning, appropriate precautions should be taken to prevent chloride (more than 50 ppm) or other contamination of finished parts prior to any processing which generates temperatures in excess of 500°F (260°C). Clean gloves may be necessary for handling of parts to make sure that this requirement is met.
NOTE:
Fingerprints can contain more than 50 ppm chloride.