210 likes | 412 Views
Alcohol in Gasoline: Some Implications in Aluminum Fuel Tanks. Kenneth M. Smith, Jr., P.E. Michael J. Danko, E.I.T. Engineering Systems Inc. 3851 Exchange Avenue kmsmith@esi-il.com Aurora, IL 60504 www.esi-website.com
E N D
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@esi-il.com Aurora, IL 60504 www.esi-website.com V: 630-851-4566 x287 F: 630-851-4870 Cell: 630-240-2048 IBEX
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 IBEX
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! IBEX
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) IBEX
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 IBEX
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 IBEX
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 IBEX
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 IBEX
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 IBEX
Specific conditions • Dissolves seawater • Promotes general corrosion Observed in laboratory IBEX
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 IBEX