Long term storage of diesel
http://amsca.com/files/Download/Fuel_news_long_term_storage_diesel.pdf

http://www.lcbamarketing.com/long_term_fuel_storage.htm

Waste vegetable oil reacts with copper to form a "greenish slime".

Material compatibility
Free fatty acids in WVO can have a detrimental effect on metals. Copper and its alloys, such as brass, are affected.
Zinc and zinc-plating (galvanization) are stripped by FFA's and tin, lead, iron, and steel are affected too.
Stainless steel and aluminum are generally unaffected.