Stainless steels (SS) are alloys developed as corrosion resistant materials. 304 SS is the most commonly used grade of stainless steels. Based on the great importance of grain boundaries and grain size due to their significant effects on the physical and mechanical behavior of alloys, corrosion behavior of 304L SS with different grain sizes was studied. Samples with different grain sizes were fabricated through formation of strain-induced martensite by 80% cold rolling of the stainless steel sheet at -15°C and its reversion to austenite during annealing at 900°C for 1, 1.5, 5, 60 and 180 min. Microstructural features were revealed by scanning electron microscopy and optical microscopy. Ferritoscope and x-ray diffraction techniques were used to identify phases and tracing phase transformation. The general and local corrosion behaviour of 304L SS with different grain size size were investigated by electrochemical tests carried out in freely aerated 0.1 M hydrochloric acid (HCl) at room temperature using a conventional three electrode cell including a Pt electrode as the auxiliary electrode, a KCl saturated Ag/AgCl reference electrode and the samples as working electrode (1 cm 2 exposed surface). The ??-martesite phase increased during rolling till the microstrucre was fully martensitic. More thickness reduction resulted in destroyed ??-martesite structure. Annealing resulted in an equiaxed grain structure of reversed austenite with grain sizes of about 0.5, 1, 3, 7 and 12 µm. Linear and Tafel polarization showed no differences in uniform corrosion rates of the samples. The results of cyclic polarisation and immersion tests showed that decreasing grain size leads to higher pitting potentials and improved local corrosion resistance. Electrochemical impedance spectroscopy and Mott-Schottky tests revealed more stable and less defective oxide layer with garin refinement. Key words : corrosion behavior, 304L, grain size, hydrochloric acid