Diesel Soap Tech Bulletin - April 2012
Peter M Guerra
Background
A new troubling phenomenon is occurring at times with Ultra Low Sulfur Diesel Fuel.The problem is called diesel soaps formation.Although not a wide spread problem yet,diesel soaps form when they react with surface active agents such as corrosion inhibitors.
Basically, The corrosion inhibitors that are added by the oil refiners at the rack contain salts that when exposed to water become acidic (actually the salt which is an acid combined with a base chemical separate into ions) These acids : (Dodecenyl succinic and Hexadecenyl succinic acid) react with fuel contaminants to form (soap like impurities) This was never a problem until the introduction of ULSD since these products were held in solution by the higher sulfur diesel fuels. With ULSD they can separate out and react with cations (eg sodium, calcium and other metal salts) commonly found in fuel tank water bottoms. Additionally rust and dirt may provide exchange sites that exacerbate the soap formation process.

