The present paper describes fuzzy logic simulation of an experimental study on the behavior of hot corrosion in molten salt (Na2SO4) of steel-T21 coated by simultaneous yttrium-doped aluminizing-siliconizingprocess . Diffusion coating was carried out at 1050oC for 6 hr under Aratmosphere . The weight change measurements made on the coated steel during the cyclic tests are used to determine kinetics of hot corrosion at temperature range (800-1000oC) for 100 hr at 5 hrcycle .X-ray diffraction and optical microscope are used to characterize the oxide phases where the oxide phases that formed on coated system are SiO2 and Al2O3 .The parabolic rate constants (Kp) calculated show that the corrosion rate is minimum at 800oC compared to other temperatures. The experimental results, the fuzzy logic model, and the statistical results showed good correlations.The fuzzy logicmodels are developed using Matlab toolbox functions.