<p>Heterostructured (HS) materials have emerged as a promising strategy to overcome the strength-ductility trade-off in metallic materials. However, their corrosion behavior, particularly when fabricated via laser cladding, remains less understood. This study investigates the microstructural evolution and corrosion behavior of 304L stainless steel fabricated by laser cladding to form a heterostructured "sandwich" (HS sample) and a bulk additively manufactured (AM) sample. The results indicate that the laser-clad samples exhibited inferior pitting resistance compared to the rolled and annealed 304L substrate in a 3.5 wt.% NaCl solution, with the AM sample performing the worst. This degradation is primarily attributed to micro-segregation-induced Cr-depleted zones and an unfavorable grain boundary character distribution, specifically a significant reduction in Σ3 twin boundaries and a high fraction of low-angle grain boundaries, which facilitated pit initiation and propagation. Interestingly, the ultra-fine grained (UFG) zone in the HS sample, despite its lower Σ3 fraction, showed relatively improved passivation behavior compared with the AM sample. This behavior is likely associated with its finer and more homogeneous microstructure and the high density of grain boundaries, which may facilitate short-range Cr transport and local repassivation.</p> Graphical abstract <p></p>