Material Compatibility of AISI 304 Stainless Steel with Diesel Fuels Containing Borate Esters

Abstract

Fuel additives should be evaluated not only in terms of their effects on engine performance and emissions, but also regarding
their compatibility with fuel storage and distribution materials. In this study, the material compatibility of AISI 304 stainless
steel with diesel fuels containing borate esters was investigated. Trimethyl borate, triethyl borate and triisopropyl borate
were blended with diesel fuel at volumetric concentrations of 0.5%, 1% and 2%. Immersion corrosion tests were carried out
at room temperature for 1000 h in accordance with ASTM G31-21, using one stainless steel specimen for each fuel
condition. Corrosion rates were calculated based on mass loss measurements, while post-immersion Fe, Cr, Ni and Mn
concentrations in the fuel phase were quantified by inductively coupled plasma mass spectrometry (ICP-MS). The highest
corrosion rate was obtained for neat diesel fuel, whereas all borate ester–diesel fuel blends exhibited lower corrosion rates.
The minimum corrosion rate, 0.000670 mm/year, was observed for TEB2 and TIB2, corresponding to an approximately
3.5-fold reduction compared with neat diesel. Post-immersion ICP-MS concentrations were also lower in the additive-
containing fuels, with the lowest total concentration measured for TIB2, indicating improved compatibility with AISI 304
stainless steel. These findings suggest that borate ester additives, particularly triethyl and triisopropyl borate at the tested
2% concentration, may help limit corrosion-related metal dissolution and improve the compatibility of diesel fuel with
stainless steel components.