What is alkaline welding rod? What is acid welding rod?

Based on the properties of their coating, welding rods can be divided into two categories: acidic and basic.

Welding rods with a coating containing a high amount of acidic oxides (such as TiO2 and SiO2) are called acidic electrodes. Acidic electrodes can be used with both AC and DC currents and offer excellent welding performance, low arc and spatter, good slag fluidity, easy slag removal, and aesthetically pleasing welds. However, due to the high content of silicates, iron oxide, and titanium oxide in the coating, they are highly oxidizing. However, the mechanical properties of the weld, especially impact toughness, are poor. These electrodes are suitable for welding general low-carbon steel and low-strength low-alloy structural steels, making them the most widely used.

Basic electrodes with a coating containing a high amount of basic oxides (such as CaO and Na2O) are called basic electrodes. The welding rod mainly relies on carbonates (such as CACO3 in marble) to decompose CO2 as a shielding gas. The partial pressure of H in the arc column atmosphere is low, and the CAF2 in fluorite combines with H to form hydrogen fluoride HF at high temperatures, thereby reducing the hydrogen content in the weld. Therefore, the alkaline welding rod is also called a low-hydrogen welding rod. The amount of CAO in the alkaline slag is large, the slag has a strong S removal ability, and good resistance to thermal cracking. Due to the low O and H content and less non-metallic impurities, it has higher plasticity and toughness, and better resistance to cold cracking; however, because the coating contains more CAF2, which affects gas ionization, alkaline welding rods generally require a DC power supply and are welded using the reverse connection method. Only when an arc stabilizer is added to the coating can AC power be used for welding. Alkaline welding rods are mainly used for welding important structures (such as boilers, pressure vessels, and alloy structural steels).