(4)  
Remove interfering fuel tank equipment, support brackets, and substructure as necessary to improve accessibility.

(5)  
Starting at outboard end of fuel tank and working inboard, direct steam at an angle of approximately 45 degrees to surface to be cleaned from a distance of 6 to 10 inches. Float foreign material toward inboard end and out sump drain valve opening.

(6)  
Check that tank is free of all loosened fungus

(7)  
Mop up all residual water.

(8)  
Ventilate with air movers until tank is dry (approximately 3 hours). Use same equipment as for purging ventilation (Ref 28-10-0 MP).

(9)  
Check all fuel tank surfaces for corrosion and remove it if found.

(a)  
Light surface corrosion can be removed by rubbing surface with fine abrasive paper or cloth.

(b)  
If corrosion cannot be fully removed by abrasive paper or cloth, use a mechanical removal method such as dry abrasive blasting with glass beads to remove corrosion -caused below surface pits (Ref Structural Repair Manual, Chapter 51, General Repair Procedures).

CAUTION:  USE STRUCTURAL REPAIR MANUAL TO ASSESS POSSIBLE STRUCTURAL WEAKENING DUE TO PENETRATION OF CORROSION AND REPAIR STRUCTURE AS NECESSARY.
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(10)
Check fuel tank for sealant damage and repair as necessary (Ref 28-11-0 AR).

(11)
Check fuel tank for damage to corrosion resistant finish and repair as necessary (Ref par. 3., this section).

D.  Return Airplane to Normal
(1)  
Remove all foreign material, tools, solvent containers, rags and brushes remaining in tank from cleaning and repair operations.

(2)  
Install any substructure, support brackets, and fuel tank equipment which was removed.

(3)  
Install fuel sump drain valve (Ref 28-11-21 R/I).

(4)  
Install fuel tank access panels (Ref 28-11-11, 28-11-31 R/I, as applicable).

3.  Application of Corrosion Resistant Finish
A.  Corrosion resistant finish is applied as a protective coating to fuel tank internal structural surfaces, especially bottom and lower sides of tank.
(1)  
BMS 10-20 type II and MIL-C-27725 are two kinds of corrosion resistant material which are approved for internal fuel tank use. An advantage of BMS 10-20 type II finish material is that additional BMS 5-26 sealant repairs may be made, if necessary, after application of the finish material provided it is fully cured by heat per Fig. 703 before the sealant is applied. The MIL-C-27725 and non-heat cured BMS 10-20 material can only be used as a topcoat after any sealant installation is complete.

(2)  
After corrosion removal, a zinc rich protective coating is preferred in addition to the BMS 10-20 coating. The complete zinc rich coating includes a primer coat of heat cured BMS 10-20 (Fig. 702, using only CURE TIME PRIOR TO SEALING), a coat of zinc rich epoxy primer and a topcoat of BMS 10-20. For local touch up and general refinishing, the primer coat of BMS 10-20 may be omitted.

B.  Equipment and Material
(1)  
Tape, Pressure Sensitive - 3M No. 250, 1-inch width, Minnesota Mining and Mfg. Co.

(2)  
Scrapers-(for removal of loose paint) wood or plastic

(3)  
Abrasive paper - 100 to 400 grit aluminum oxide, wet or dry

(4)  
Abrasive discs - 100 to 400 grit, 3M Scotchbrite, Minnesota Mining and Mfg. Co.

(5)  
Abrasive pad (Ref 20-30-51)

(a)  
Aluminum oxide abrasive - Scotch Brite Sheet, TYPE A.

(b)  
Aluminum oxide nylon pad, TYPE F.

(c)  
Aluminum oxide - Bear-Tex

(d)  
Aluminum oxide - Microlon

(6)  
Cleaning Solvent (Ref 20-30-31)

(a)  B01013 Cleaning Solvent, Final Cleaning Prior to Fuel Tank Sealing (Series 93) Ref AMM/SOPM 20-30-93)
WARNING:  DO NOT GET SOLVENT IN YOUR MOUTH, EYES, OR ON YOUR SKIN. DO NOT BREATHE THE FUMES FROM SOLVENTS. SOLVENTS ARE HAZARDOUS MATERIALS. REFER TO PRODUCT MATERIAL SAFETY DATA SHEET (MSDS) AND LOCAL REQUIREMENTS FOR PROPER HANDLING PROCEDURES.
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(7)  
Cleaning cloths - all material should contain less than 0.75% oil by carbon tetrachloride extraction

(a) 
 Cheesecloth

(b)  
Unsterilized gauze pads

(c)  
White rags

(8)  
Explosionproof air blower, with sufficient flexible hose to reach all areas in the fuel tanks. The capacity must be 90-100 cubic feet per minute (Rhine Air, Inc., 10744 Prospect Avenue, Suite A, Santee, CA 92071)
　
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