High school electrochemistry for the understanding of metal protection

The anode loses electrons and the cathode gains electrons.

A sacrificial anode uses a metal that is more reactive than the metal being protected so that it reacts first and loses electrons so that the metal being protected is not corroded. When the more reactive metal is corroded, the protective effect is gone.

The impressed current is also the loss of electrons by replacing the protected metal with the applied electrons.

It's all so good, what should I do!

Non-polluting or less polluting. Electrochemistry.

The resulting process reacts directly and selectively with organic pollutants in the wastewater, degrading them to carbon dioxide.

Water and simple organic matter, with little or no secondary pollution. Electrons are the main reactants of electrochemical reactions, and electron transfer is only carried out between the electrode and the waste components, without the addition of any oxidants or reducing agents.

Secondary contamination caused by the addition of chemicals is avoided, and the electrode reaction can be highly selective by controlling the potential to prevent side reactions.

It has a high degree of flexibility. Electrochemical technology has multiple functions such as air flotation, flocculation and sterilization, and if necessary, the cathode and anode can play a role at the same time. It can be used as a stand-alone treatment process or combined with other treatment processes, such as as as a pre-treatment, which can convert refractory organic matter or biotoxic pollutants into biodegradable substances, thereby improving the biodegradability of wastewater.

According to the principle of electrochemical corrosion, it is a material protection technology that relies on the inflow of external current to change the potential of the metal, thereby reducing the corrosion rate of the metal.

Technique. According to the trend of metal potential change, electrochemical protection is divided into two categories: cathodic protection and anodic protection. Cathodic protection.

The purpose of protection is achieved by reducing the metal potential, which is called cathodic protection. According to the protection current, cathodic protection has the impressed current method and the sacrificial anode method. The impressed current method is to provide protection current from an external DC power supply, the negative pole of the power supply is connected to the protection object, and the positive electrode is connected to the auxiliary anode, forming a current loop through the electrolyte environment.

The sacrificial anode method relies on the potential negative to the metal (sacrificial anode) of the protected object to provide protection current, and the protection object is directly connected to the sacrificial anode to form a protective current loop in the electrolyte environment. Cathodic protection is mainly used to prevent metal corrosion in neutral media such as soil and seawater. Anode protection.

The purpose of protection is achieved by increasing the potential of the passivable metal to bring it into a blunt state, which is called anodic protection. Anode protection is the use of anodic polarization current to keep the metal in a stable blunt state, and its protection system is similar to the impressed current cathodic protection system, except that the direction of the polarization current is opposite. Only corrosion systems with activation-passivation transitions, such as concentrated sulfuric acid tanks, ammonia water tanks, etc., can be protected by anodic protection technology.

A material protection technology that inhibits or reduces corrosion of metal structures by changing the polarity or moving the anodic polarization potential of the metal to the passivation region.

Looking at the two metal electrodes of a Gafany battery, corrosion always occurs on the anode. Cathodic protection is the use of sacrificial anodes (such as zinc, aluminum, etc.) or an inert anode with an impressed current in moist soil or water containing electrolytes (such as salts, etc.) to make the protected steel structure the cathode in this artificial Gaphani battery. In the same corrosive environment, the greater activity is the anode, and the smaller is the cathode, for example, in seawater, if the electrolytic battery is formed between zinc and mild steel, zinc is the anode, and steel is the cathode; But if steel and stainless steel form an electrolytic cell, the steel becomes an anode, and stainless steel is the cathode.

The cathode is actually an electrode that reduces the cations in the electrolyte by gaining electrons. Therefore, the use of an external DC power supply to make it electronically replenished is also a cathodic protection method. The required protection current density varies depending on the corrosive media.

Steel is in soil, about a decimeter, in flowing seawater, and in flowing freshwater.

According to the principle of electrochemical corrosion, it is a material protection technology that relies on the inflow of external current to change the potential of the metal skin, thereby reducing the speed of metal corrosion. Qing Wangcha.