(b) If you cannot fully remove the corrosion with a wire brush, use a mechanical removal procedure (Ref SRM). 1) For example, you can hit the surface with some dry abrasive
glass beads to remove corrosion below the surface.
S 217-019
(15)
Look in the fuel tank for areas with loose corrosion resistant finish (topcoat).
S 167-037
(16)
If you find some loose corrosion finish, do these steps to remove it:
(a)
Remove all the loose finish with a wood or plastic scraper.
(b)
Clean the structure with a stainless steel brush that turns or with a wire brush that you hold in your hand.
(c)
Use pressure sensitive tape to do a check for loose finish of the surfaces adjacent to the areas with loose finish. 1) Apply a strip of the pressure sensitive tape to do a test
of the surface.
2) Push the tape down tightly with an equal and constant
pressure.
3) Push down tightly on the full strip of tape.
4) Remove the tape from the surface in one quick movement away
from the surface. 5) Examine the surface and the tape for removed finish or loosened finish.
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6) If you find some removed finish or loosened finish, remove all damaged finish from the surface.
(d)
Use the tape to do a check of other areas that can have loose finish.
(e)
Clean the area with a vacuum cleaner to remove the flakes of the used finish and other unwanted material.
S 397-020
(17)
Repair the areas with damaged sealant or sealant that is not there (AMM 28-11-00/801).
S 377-021
(18)
Repair the areas where the corrosion resistant finish (topcoat) is not there or was removed (AMM 28-11-00/801).
G.
Put the Airplane Back to Its Usual Condition
S 097-022
(1)
Remove all this remaining unwanted material:
(a)
Tools
(b)
Solvent containers
(c)
Rags
(d)
Brushes
(e)
Other unwanted material that you used to clean the tank and repair the tank.
S 417-023
(2)
Install the support brackets and the fuel tank equipment that you removed.
S 417-024
(3)
Install the primary poppet valve in the sump drain valve
(AMM 28-11-04/401).
S 417-025
(4)
Install the secondary poppet valve in the sump drain valve
(AMM 28-11-07/401).
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S 417-026
(5) Go out of the fuel tank and close it (AMM 28-11-00/201).
TASK 28-11-00-307-182
7. Apply the Corrosion Resistant Finish (Topcoat) (Fig. 702)______________________________________________
A. General
(1)
Corrosion resistant finish (topcoat) is applied to prevent corrosion to the internal structural and tubing surfaces, especially the bottom and lower sides, of the fuel tank. BMS 10-20 Type II and MIL-C-27725 are two types of corrosion resistant material which are approved for internal fuel tank use. An advantage of BMS 10-20 Type II finish material is that you can make additional BMS 5-26 or BMS 5-45 sealant repairs, if necessary, after you apply the finish material if it is fully heat cured before sealant is applied. The MIL-C-27725 material can only be used as a topcoat after the sealant installation is complete.
B.
References
(1)
AMM 12-11-01/301, Fuel Tank Servicing
(2)
AMM 20-30-81/201, Airplane Structure Cleaning Solvents (Series 81)
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