Dew corrosion

The following can be used: 1. Heat preservation treatment； 2. Apply protective coating ； 3. Cathodic potential protection ；

What is cathodic potential protection?

Cathodic protection is an electrochemical protection technique used to prevent metal from corroding in dielectrics such as seawater, fresh water, and soil. The basic principle of this technique is to use the metal component as a cathode and apply a certain direct current to it, thereby causing cathodic polarization. When the potential of the metal becomes more negative than a certain value, the electrochemical unevenness on the surface of the metal is eliminated, and the process of cathodic dissolution that leads to corrosion is effectively suppressed, thus achieving the purpose of protection. 　　The protected metal gains an excess of electrons, which prevents corrosion; as a result, no oxidative chemical reactions occur on its surface. 　　Two methods of cathodic protection: 1) Sacrificial anode method. The sacrificial anode method involves using metals or alloys with a low electrical potential (such as magnesium alloys, zinc alloys, aluminum alloys, etc.) as anodes; these are connected to the metal to be protected through a medium such as seawater, thereby creating a battery effect. While the cathode (the structure to be protected) is protected, the anode is continuously consumed, which is why it is called a sacrificial anode. 2) Forced current method The forced current method (external current method) involves applying a cathodic current to the structure to be protected, while applying an anodic current to a auxiliary anode (usually high-silicon cast iron or scrap steel), thereby creating a corrosion cell. Metal structures are protected using the same principle. Zinc Zinc has proven to be a very effective anode material for cathodic protection. Zinc anodes have strict requirements regarding trace harmful elements in zinc ingots. Traditional zinc anodes contain aluminum, and cadmium must be added to them in order to overcome adhesion. Compared to the protected steel structure, the zinc anode has a driving potential of 220 mV. The capacitance of the zinc anode is 780 A·h/kg. Zinc anodes are highly suitable for protecting coating structures with low current. Aluminum: Theoretically, aluminum has a very high capacitance as a material for sacrificial anodes. In fact, aluminum alloys are used by various companies as a new type of anode material to replace zinc anodes. Since their introduction in 1960, aluminum alloys containing zinc and indium have proven to be very reliable and effective anode materials. The aluminum anode has a driving potential of 300 mV with respect to the protected steel structure, and the current capacity of aluminum alloys is 2700 A·h/kg. Magnesium: As a new type of anode material, magnesium is used in marine engineering applications with special requirements, such as ship hulls in fresh water and ballast tanks containing fresh water.

General cold insulation treatment, coating application.