Experimental investigation on the corrosion and corrosion fatigue behavior of butt weld with G20Mn5QT cast steel and Q355D steel under dry–wet cycle

•Chloride ions erosion, defects and drying time affect the pitting corrosion greatly.•Casting, welding defects and pitting cause fatigue failure at different stress levels.•S-N curve is developed based on three-parameter Weibull model with good applicability.•Dry-wet cycle accelerates corrosion fatigue crack initiation and propagation.•The corrosion fatigue mechanism under dry-wet is the same as that in full immersion. Corrosion and corrosion fatigue experiments were conducted on a butt weld constructed of G20Mn5QT cast steel and Q355D steel in a dry–wet cycle with 3.5 wt% NaCl solution. The microstructural characterization was analyzed using SEM. The butt weld suffered from pitting corrosion in a dry–wet cycle. Chloride ion erosion and defects (welding defects and casting defects) have important influences on pitting corrosion. Internal defects and corrosion pits are the main cause of corrosion fatigue failure of the butt weld specimens. Drying time accelerates pitting corrosion and corrosion fatigue progression without changing the corrosion and corrosion fatigue mechanism in 3.5 wt% NaCl solution. The three-parameter Weibull model has good applicability for evaluating the corrosion fatigue behavior of G20Mn5QT cast steel and Q355D steel butt welds in simulated seawater.