Preliminary Requirements

Procedure

1. SUBTASK 70-38-09-340-001 Prepare the Parts to be Aluminized

   1. Clean the parts.

      1. Use one of the two vapor degrease or the solvent cleaning procedure - (Refer to the SPM TASK 70-11-01-300-503 or SPM TASK 70-11-33-300-503).

   2. Make all the surfaces rough which are to be aluminized. Use steel or No.24-100 abrasive grit or acid pickling unless told differently. If compressed air is used, it must have no oil and water contamination.

   3. Use high pressure clean dry air to clean the surfaces which have been made rough. Remove all the dust and particles. The surfaces to be aluminized must be kept clean. You must use gloves if you touch the parts.

   4. Apply the aluminum coating as soon as possible after the surfaces have been prepared.

2. SUBTASK 70-38-09-340-002-001 Apply the Aluminum Coating

   1. Use CoMat 03-252 WIRE, SPRAY-ALUMINUM. Alternative consumable materials can be used.

   2. Apply masking tape to the part as necessary.

   3. Apply the aluminum coating. Use a minimum of operations. Do not apply the aluminum coating in one operation.

   4. Use the subsequent data to apply the aluminum coating.

      1. Natural gas or propane:

         1. Pressure regulator: 30 to 33 psi (206.8 to 227.5 kPa).

         2. Flow meter: 25 to 30.

         3. Gun distance: 5 to 8 in. (127 to 203 mm).

      2. Oxygen:

         1. Pressure regulator: 32 to 34 psi (220.6 to 234.4 kPa).

         2. Flow meter: 38 to 48.

      3. Air:

         1. Pressure regulator: 60 to 65 psi (413.7 to 448.2 kPa).

   5. The metal spray gun or the part must have movement when the aluminum coating is applied. Do not let the two stay in a stopped position.

3. SUBTASK 70-38-09-340-002-002 Apply the Aluminum Coating

   1. Put the part fully into liquid aluminum, which must have a minimum purity of 99 percent.

4. SUBTASK 70-38-09-340-002-003 Apply the Aluminum Coating

   1. NOTE

      The metal content of the slurry or the paint must not be less than 99 percent aluminum. A maximum of 5 percent of iron or nickel can be used instead of aluminum.

      Use a suitable aluminum slurry or paint. This can be applied by spray, brush, or dipping. (Refer to the SPM TASK 70-38-09-100-501).

   2. Use a wetted-down paint brush to do the paint brush process. Use a minimum of two or more operations. Do not apply the aluminum slurry in one operation. Do the spray gun process in a number of operations to apply the correct thickness of aluminized paint slurry.

   3. 

      CAUTION

      DO NOT USE A VACUUM AS THE PROTECTIVE ATMOSPHERE. THE ALUMINUM COATING WILL BECOME A GAS AND DISAPPEAR AT THIS TEMPERATURE IN A VACUUM.

      NOTE

      Step C. is not necessary if the increase in temperature in Step is sufficiently slow to give a temperature of 1150 to 1450 deg F (621 to 788 deg C) for 7 to 10 minutes.

      Prediffuse the parts at 1335 to 1365 deg F (724 to 741 deg C) for 7 to 10 minutes. Use a pure dry hydrogen atmosphere with a dew point of -40 degrees or better. The pure dry hydrogen must have a zero percent oxygen content.

   4. Reduce the temperature of the parts to room temperature.

   5. Clean the parts. Use a high pressure.

   6. Examine the aluminum coating for pits or holes (eutectic melting).

5. SUBTASK 70-38-09-340-002-004 Apply the Aluminum Coating

   1. Use a pack cementation procedure.

6. SUBTASK 70-38-09-340-003 Diffuse the Aluminum Coating

   1. 

      CAUTION

      DO NOT USE A VACUUM AS THE PROTECTIVE ATMOSPHERE. THE ALUMINUM COATING WILL BECOME A GAS AND DISAPPEAR AT THIS TEMPERATURE IN A VACUUM.

      Diffuse the aluminum coating. Increase its temperature in a protective atmosphere. (Refer to the applicable engine manual).

7. SUBTASK 70-38-09-120-001 Clean the Aluminum Coatings

   1. Clean all the unwanted oxides and scale from the aluminum coatings. Use a wet abrasive blast procedure.

8. SUBTASK 70-38-09-220-001 Examine the Aluminum Coating

   1. The aluminum coating thickness must be 0.001 to 0.003 in. (0.03 to 0.08 mm) unless specified differently.

   2. Increase the temperature of a sample part, in air, to 1500 deg F (816 deg C) for one hour. Make sure there is no dark oxide on the aluminum coating.

   3. The aluminum coating must have a constant thickness. There must be no pin holes, scratches, cracks, crazing, or spalling.