Effect of MnS inclusion dissolution on carbon steel stress corrosion cracking in fuel-grade ethanol

• We measured MnS dissolution rates in fuel-grade ethanol with hydrochloric and acetic acid.
• We measured the dissolution rate of MnS inclusion inside intergranular SCC crack.
• The MnS dissolution products were detected in fuel-grade ethanol.
• It was found that the conditions inside intergranular SCC crack are not very acidic.

The intrinsic dissolution rate of manganese sulfide (MnS) was measured in water with hydrochloric acid and in fuel-grade ethanol (FGE) with acetic acid and hydrochloric acid using static disk system. The intrinsic dissolution rate of MnS is used to evaluate conditions inside the intergranular stress corrosion cracks (SCC) by studying partially dissolved MnS inclusions on intergranular SCC fracture surfaces of failed carbon steel piping handling FGE. The penetration rate of MnS inclusion dissolution front was measured to vary from 11 μm/year up to 127 μm/year inside the cracks. According to the results the conditions inside intergranular SCC crack are not acidified.