Importance of corrosion-resistant castings

       Metals and their alloys are still considered to be the most important structural materials, so < a="" class="{$$0$$}">Corrosion-resistant castings naturally become one of the most interesting questions. Depending on the type of corrosion damage, the causes of other influencing factors are different under various environmental conditions. In order to mitigate and prevent corrosion damage and its loss, corrosion resistant castings have also been developed by changing certain actions to prevent and control corrosion process conditions and influencing factors.

       Wet corrosion refers to corrosion of metal in the presence of moisture, dry corrosion means Corrosion in dry gas without large amounts of liquid waterSince the atmosphere generally contains water, chemical formation is often in contact with various moisture solutions, so wet corrosion is very common, but damage caused by dry corrosion during high-temperature operation cannot be ignored.

       metal in Corrosion in an aqueous solution is an electrochemical reaction. An etch cell having anode and cathode region isolation is formed on the metal surface. The metal loses electrons in the solution and becomes positively charged ions, which is an oxidation process or an anode process. At the same time, when in contact with the metal surface of the aqueous solution, the electrons are likely to be neutralized by the substances in the solution, and the process of neutralizing the electrons is a reduction process, that is, a cathode process. Common cathode processes are aerobic reduction, hydrogen evolution, oxidant reduction and precious metal deposition.

       in high temperature oxidation Often corrosion-resistant castings are common in high temperature gases. In the high temperature gas, an oxide film is formed on the metal surface. The nature and growth of the film determines the corrosion resistance of the metal. The growth law of the membrane can be divided into linear law, parabolic law and logarithmic law. Straight line oxidation is the most dangerous because metal weight loss increases at a constant rate over time. The rule for parabolic and logarithmic is that the rate of oxidation decreases with increasing film thickness and is safer.