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An Alternate Corrosion Resistant Coating to be Applied to Aluminum Secondary Power System Parts

Description:

TECHNOLOGY AREA(S): Materials 

OBJECTIVE: Identify and qualify a corrosion resistant coating applicable to aluminum gearboxes, covers and other Secondary Power System parts. New corrosion resistant coating shall surpass the current conversion coating which is slightly better protection than having no coating at all. 

DESCRIPTION: Secondary Power Systems Office is involved with multiple weapon systems including: A-10, B-1, B-2, C-130, E-3, F-15, F-16, KC-135, T-38. This office manages large housings, auxiliary power units (APU), aircraft mounted accessory drives (AMAD), Fuel control units, Emergency Power Units (EPU), Jet Fuel Starters (JFS), Hydraulic Starter Motors (HSM), and Central Gearboxes (CGB). Many of these assets are very complex and high in cost; therefore extending the lifecycle of these parts would contribute to mission readiness and part availability for the war fighter. A contributing factor to the condemnation and costly repairs of Secondary Power System parts is corrosion. Many of these parts are exposed to harsh environmental elements to include: high humidity (100%), low and high temperatures (-65 to 1350 °F), salt, hydro-carbons, sand, etc. The current corrosion resistant coating is anodized per MIL-DTL-5541 and Alodine coated in accordance with (IAW) MIL-DTL-71706B or MIL-A-8625 for aluminum components. Occasionally, this method does not sufficiently protect the parts from corrosion during their lifecycle. The alternative corrosion resistant coating shall allow the sufficient corrosion protection necessary to last for numerous overhaul cycles. The conversion coating not only has to be applied to newly manufactured parts but also has to be applied to overhauled parts which have been coated with anodize, Alodine, and/or paint. During the overhaul process, chemicals and aggressive media blast are used to strip paint which often times takes off the thin conversion coat. The alternative corrosion resistant coating shall be effectively applied to newly manufactured parts as well as overhauled parts. Because the Secondary Power System parts are used extensively in many different environments, many aggressive cleaning chemicals are used to sufficiently clean the assets during the overhaul process IAW technical order (TO) 2G-1-2. Some of these chemicals may include: vapor degreasers, carbon removers, and general detergents. The alternative corrosion resistant coating shall be resistant to aggressive chemicals as stated in TO 2G-1-2. Furthermore, this effort is to research and qualify one alternate corrosion resistant coating for aluminum Secondary Power System assets. Samples or coupons of cast aluminum (Alloys: 355-T61, or 5056-H18) will be coated and subjected to environmental testing to determine the best possible solution for the United States Air Force’s assets. Possible testing includes salt spray testing (ASTM B117), Abrasion Resistance (ASTM D4060), Scratch resistance (ASTM D3363), Coating adhesion (AMS 3095), and/or any other applicable testing necessary. 

PHASE I: Develop a solution that meets above requirements and conduct preliminary business case analysis (BCA) to determine implementation costs, including a return-on-investment (ROI) calculation that compares anticipated savings to expected costs. Coupons and other testing shall be performed to test the feasibility of recommended coating. 

PHASE II: Proof-of-concept prototype shall be refined to installation-ready article and shall undergo testing to verify and validate all requirements. This process may require multiple iterations before a final design is selected. Process requirements shall be well defined and provided to the government. Refine BCA/ROI based on the final design. 

PHASE III: If cost effective, qualify, transition and implement the test procedure in the production environment at the Hill Air Force Base Secondary Power facility with associated recommended technical order changes. 

REFERENCES: 

1: MIL-DTL-81706B, CHEMICAL CONVERSION MATERIALS FOR COATING ALUMINUM AND ALUMINUM ALLOYS

2: MIL-A-8625, ANODIC COATINGS FOR ALUMINUM AND ALUMINUM ALLOYS

3:  AMS 3095, Paint: High Gloss For Airline Exterior System

4: ASTM B117, Standard Practice for Operating Salt Spray (Fog) Apparatus

KEYWORDS: Corrosion Resistant, Coating, Aluminum, Secondary Power Systems 

CONTACT(S): 

Mr. Tosh Farr 

(801) 777-0927 

tosh.farr@us.af.mil 

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