Underwater wet welding is one of the techniques used in the repair of underwater oil and gas platforms, with a large expansion in the world nowadays. Its major advantage over other welding processes is due to its simplicity and ease of deployment, as it allows the diver to work directly on the submerged portions of the parts without the protection of an artificial environment, as in the traditional dry welding. Both oxidizing and rutilic electrodes are used in this type of welding. In this study we assessed the effects of the use of wustite in partial replacement of Hematite, a mineral used in the coating of oxidizing electrodes. Five groups of electrodes were produced with a fixed percentage of the total weight of iron oxide and varying proportions of FeO and Fe2O3. Four pass welds in the flat position with 60° angle of inclination between the electrode plate and a 0.5m deep were performed. Weld metals were evaluated by chemical analysis, microscopy, diffusible hydrogen and micro-hardness. Digital image analysis methods were developed to measure inclusion area fraction from OM and SEM images, and the fraction of micro-constituents by OM. The results showed an increase of proeutectoid ferrite with increasing wustite content and a decrease with increasing carbon content, which, by its turn, decreased with increasing wustite content. Micro-hardness decreased with wustite content and increased with carbon content.