Removal of fuel sulfur assumes that hot corrosion events will subsequently end in shipboard and aero gas turbine engines. Most papers in the literature since the 1970s consider Na2SO4 and SO3 as the primary reactants causing hot corrosion. However, several geographical sites around the world have relatively high pollutant levels (particulate matter, SO2, etc.) that have the potential to initiate high-temperature corrosion. The deposit chemistry influencing hot corrosion is more complex consisting of multiple sulfates and silicates with the addition of chlorides in a marine environment. Sulfur species may still enter a ship combustion chamber as contaminants via air intake or with seawater entrained in air entering through the ship air intake.
High levels of impurities (SO2) above 2 ppm can lead to hot corrosion attack. Research is needed to determine how sulfate salt mixtures and air impurities influence hot corrosion in marine and non-marine conditions. Other impurities such as phosphorus, lead, chlorides, sand, and unburned carbon may lower salt melting temperatures, alter the sulfate activity, or change the solution chemistry and acidity/basicity that leads to accelerating hot corrosion. Other issues need to be considered in non-metallic materials system.