Preliminary Requirements

Safety Requirements

WARNING

CHROMIC ACID IS VERY DANGEROUS. IF BREATHED, IT WILL CAUSE ULCERS IN THE NOSE AND IT CAN CAUSE DAMAGE TO THE NASAL SEPTUM. CHROMIC ACID SALTS AND SOLUTIONS, THAT TOUCH THE SKIN, CAN CAUSE CHROME SORES. THEY CAN ALSO CAUSE ULCERS, IF THEY GET INTO CUTS AND ABRASIONS.

WARNING

THE CHROMIUM ACID BATH MUST NOT BE USED, UNLESS THE FUME EXTRACTOR IS OPERATED AND IS FULLY SERVICEABLE.

WARNING

A RECOMMENDED BARRIER CREAM MUST ALWAYS BE APPLIED, TO THE HANDS AND FOREARMS, BEFORE WORK IS STARTED.

WARNING

PROTECTIVE CLOTHING MUST ALWAYS BE WORN.

WARNING

DO NOT EAT OR SMOKE, NEAR THE CHROMIUM PLATING BATH.

WARNING

IF CUTS AND ABRASIONS DO NOT HEAL SATISFACTORILY, TELL THE MEDICAL DEPARTMENT.

WARNING

CHROMIC ACID SOLUTION CAUSES OXIDATION AND IS A FIRE RISK, BECAUSE OF THE POSSIBLE SPONTANEOUS COMBUSTION OF ORGANIC MATERIALS - (SUCH AS CLOTH AND WOOD), SOAKED BY THE SOLUTION. SUCH DIRTY MATERIALS MUST BE SOAKED IN SODIUM BISULPHATE SOLUTION TO MAKE NEUTRAL THE CHROMIC ACID, THE SOLUTION MUST THEN BE DISCARDED AS SPECIAL UNWANTED MATERIAL. THE SOLID MATERIAL MUST THEN BE FLUSHED WITH WATER BEFORE IT IS DISCARDED.

WARNING

IT IS THE RESPONSIBILITY OF THE OPERATOR TO OBTAIN AND OBSERVE THE MANUFACTURERS MATERIAL SAFETY DATA SHEETS FOR CONSUMABLE MATERIALS INFORMATION SUCH AS, HAZARDOUS INGREDIENTS, PHYSICAL/CHEMICAL CHARACTERISTICS, FIRE, EXPLOSION, REACTIVITY, HEALTH HAZARD DATA, PRECAUTIONS FOR SAFE HANDLING, USE AND CONTROL MEASURES AND ALSO TO TAKE LOCAL REGULATIONS INTO CONSIDERATION.

CAUTION

THE ANODIZING PROCEDURE MUST BE CAREFULLY CONTROLLED, BECAUSE DAMAGE TO THE PARTS CAN BE CAUSED.

Procedure

1. SUBTASK 70-33-20-300-001 Anodic Coating Procedure

   1. Preparation of parts.

      1. Remove the organic paint from the parts, as specified in the Engine Manual.

         NOTE

         All repairs and inspections must be completed, before anodizing.

      2. Remove the remaining anodic coating, together with all corrosion, as specified in the Engine Manual.

      3. Clean the parts with kerosine - (Refer to the SPM TASK 70-11-14-300-503).

      4. When necessary, remove the grease from the parts - (Refer to the SPM TASK 70-11-01-300-503).

      5. When necessary, apply the CoMat 07-014 STOPPING-OFF LACQUER to the parts.

         NOTE

         Suspenders with titanium contact faces are recommended; although aluminium is also satisfactory.

         Suspenders made from aluminium must have the anodic coating removed, as specified in the SPM TASK 70-33-58-330-501. All contact faces must be cleaned, with a wire-brush, before they are used again.

         Jigs that have become defective, because of continuous use, must be discarded.

         If the Engine Manual instructions do not recommend a special suspender, attach the parts with aluminium wire; but always make sure that there is a good electrical connection, between the wire and the part. The wire must always be discarded, after use.

      6. Attach the parts to the applicable suspender:

      7. Remove the grease from the parts - (Refer to the SPM TASK 70-11-01-300-503), then dry in air; to remove the remaining solvent.

   2. Chromic anodize the parts.

      1. NOTE

         The solution must be constantly mixed, by a pump or with clean compressed air, to make sure that the temperature is kept constant, through the full bath.

         Put the parts fully into the chromic anodizing solution - (Refer to SUBTASK 70-33-20-100-001), at a temperature of 100 to 108 deg F (38 to 42 deg C). Install the parts so that air bubbles can not occur, then connect them to the positive pole of the DC electrical power supply; to make a good electrical contact.

      2. NOTE

         When specified in the Engine Manual the alternative anodizing procedure, that follows, can be applied. This procedure is better for aluminium alloys that are close to the maximum permitted alloy structure - (That is, a total of 7 percent copper, nickel and iron; or more than 5 percent copper).

         Apply the current so that the voltage across the bath is increased - (In maximum steps of 5 volts, from 0 to 40 volts), during the first 10 minutes. Keep at 40 volts for 20 minutes then continuously increase, from 40 to 50 volts, during the subsequent 5 minutes. Keep at 50 volts for 5 minutes then decrease, to zero volts, during the subsequent minute. These times are the minimum times permitted.

         1. With the solution temperature kept at 77 to 86 deg F (25 to 30 deg C), apply the current so that the voltage across the bath is continuously increased - (In maximum steps of 5 volts, from 0 to 40 volts), during the first 10 minutes. Keep at 40 volts for 30 minutes then decrease, to zero volts, during the subsequent minute.

      3. NOTE

         Highly porous aluminium parts - (For example castings) are better if put into clean, cold, water - (Or alternatively, hot water at a temperature of 158 deg F (70 deg C)) for a maximum of 1 hour, to make sure that all the solution is removed.

         Remove the parts from the solution, quickly drain, then fully flush in a clean, cold, water flow, until all the solution is removed.

      4. NOTE

         When dichromate sealing is specified in the Engine Manual, step (5) does not apply.

         Remove the parts from their suspenders, or wires, then do step (3) again.

      5. NOTE

         When paint is to be applied to the anodic coating - (That is, when specified in the Engine Manual), the full procedure must be completed in less than 16 hours.

         Put the parts fully into clean, hot, water at a maximum temperature of 158 deg F (70 deg C). Remove the parts and dry with clean, dry, compressed air.

   3. NOTE

      When specified in the Engine Manual, dichromate sealing must be done immediately after Step above.

      Dichromate seal the parts.

      1. Put the parts fully into the dichromate sealing solution - (Refer to SUBTASK 70-33-20-100-002), at a temperature of 204 to 212 deg F (96 to 100 deg C), for 20 minutes.

      2. Remove the parts from the solution, drain-off, then fully flush in clean, cold, water flow.

      3. Put the parts momentarily into clean, hot, water; at a temperature of 212 deg F (100 deg C). Dry-off with clean, dry, compressed air.

      4. Let the parts become cool. When necessary, remove the stopping-off lacquer with CoMat 01-076 METHYL ETHYL KETONE.

   4. Examine the parts.

      NOTE

      A chromate conversion coating - (Refer to the SPM TASK 70-38-02-300-503) can be used to give protection against corrosion; to small areas where the anodic coating is damaged, or is not complete.

      The anodic coating must only be removed from the parts, when specified in the Engine Manual.

      1. Examine the anodic coating, to make sure it is continuous and free from defects. More inspection checks must be done, when specified in the Engine Manual.