Fig. 3: The corrosion morphologies on welded joint.

a, b The corrosion morphologies on the BM surface in acidic soil solution without riboflavin; c, d the corrosion morphologies on the HAZ surface in acidic soil solution without riboflavin; e, f the corrosion morphologies on the WZ surface in acidic soil solution without riboflavin; a′, b′ the corrosion morphologies on the BM surface in acidic soil solution with 10 ppm riboflavin; c′, d′ the corrosion morphologies on the HAZ surface in acidic soil solution with 10 ppm riboflavin; e′, f′ the corrosion morphologies on the WZ surface in acidic soil solution with 10 ppm riboflavin.