Alcohol%20in%20Gasoline:%20%20Some%20Implications%20in%20Aluminum%20Fuel%20Tanks

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Alcohol in Gasoline Some Implications
inAluminum Fuel Tanks

• Kenneth M. Smith, Jr., P.E.
• Michael J. Danko, E.I.T.
• Engineering Systems Inc.
• 3851 Exchange Avenue            
   kmsmith_at_esi-il.com
• Aurora, IL 60504                       
  www.esi-website.com
• V 630-851-4566 x287 F 630-851-4870 Cell
  630-240-2048

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Engineering Systems Inc.

• Engineering consulting firm specializing in
• Research and consulting
• Forensics, Accident investigation
• Many engineering disciplines
• Materials, Mechanical, Electrical, Biomechanical
• Commercial Marine, Civil, Structural, Marine
• Marine Research focus at Ft. Myers, FL

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Gasoline

• Gasoline is not uniformly formulated product
• Formulation varies brand to brand
• Season to season
• State to state
• Sometimes day to day
• E-10 (10 ethanol) is mandated in many mid-west
  states
• Results not uniform
• for all products!

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Aluminum Fuel Tanks

• USCG, ABYS, NMMA approved and commonly used
  especially in larger yachts
• Good history in service
• Good value and many good properties wrt gasoline
  tankage.
• Does E-10 affect tank performance?
• (Lab tests, sea salt water and AL5052)

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Corrosion

• Surface protection is automatic
• Aluminum oxide formation
• Galvanic corrosion potential when
• Electrolyte (conductive medium)
• Dissimilar metals present
• Most vulnerable areas
• If metals contaminate tanks
• Near welds

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Mechanism

• Dissimilar metals form a battery
• Local anodes and cathodes
• Current flows through metal
• Cathodes sacrifice metal into liquid as ions
• Local metal loss, pitting potential
• Must have a conductive liquid electrolyte

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Corrosion Sites

• Where water phase pools under gasoline
• At the water-gasoline interface
• Near dissimilar metal or contamination site
• Accelerated with Cu
• for these tests
• of Al 5052

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E-10 Holds Water

• How much --Depends on
• Temperature
• Hydrocarbons in the gasoline blend (aromatics and
  others)
• Alcohol blend
• Co-solvents in the gasoline. Often blended with
  TBA
• More alcohol in blend
• holds more water

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Affects of E-10 on Corrosion

• Carries more water (including salt water) into
  solution or suspension
• Apparently concentrates salt in water phase when
  second phase forms

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Specific conditions

• Dissolves seawater
• Promotes general corrosion
• Observed in laboratory

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Conclusions

• E-10 introduces slight increase in corrosion
  potential in aluminum tanks
• Requires a combination of unusual factors
• Salt water contamination (long term)
• Contamination of tank with solids
• May be possible to passivate surfaces to reduce
  corrosion potential further
• Requires focused research

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  Brand A Brand B    
Coupon Salt Water Salt Water Corrosion rate 0.1 mils/yr Pit Depth (mils)
1 20   1.4 8.5
2 20   1.4 7.5
3 20   1.1 11.6
4 10   0.9 13.4
5 10   0.9 13.2
6 10   0.8 12.6
7 7   1.1 11.4
8 7   0.9 10.2
9 7   0.9 8.7
10 5   1.2 13.4
11 5   1.1 9.3
12 5   1.8 6.7
13 1   1.6 12.9
14 1   1.1 9.4
15 1   1.1 9.3
16 0   0.0 --
17 0   0.0 --
18 0   0.0 --
19   10 0.1 --
20   20 0.1 --
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