corrosion mechanism of steel structures in marine environment

Guangzhou Steel News: corrosion mechanism of steel structures in marine environment

Electrochemical corrosion mechanism of steel in the marine environment
 
The marine environment can be divided into several categories: marine atmospheric zone, splash zone, the water level fluctuation zone, immersion zone and area under the mud. Steel same process of electrochemical corrosion cell reaction with the electrolyte in the five regions, three elements constitute the reaction of the anode, cathode and electrolyte conductivity.
 
In the anode region, the ferrite is precipitated iron ions into the solution so that the active metal is dissolved. In the cathode region, when the PH value of the solution is less than 4, the product of the anode and the cathode product iron hydroxide ions combine to produce corrosion products precipitated ferrous hydroxide, ferrous hydroxide is oxidized by oxygen in solution, converted to hydrogen iron oxide (ie rust).
 
Thermodynamic Principles of steel corrosion in marine environment
 
Metal elements and non-metallic elements in nature there is one of the most stable state, that is the lowest energy state. If you change the state of the element by a chemical or electrochemical method, making it a higher energy state, the element has the energy to return to a stable state, the conditions are right they spontaneously return to the original state. The water referred to a higher position, the water will have a return to the lower energy, once the conditions are right, water flows spontaneously from the lower height, restored to its original state.
 
Guangzhou Steel summary; steel is made of iron, and iron with coke carbon hematite (Fe2O3) reduction obtained. Rust is iron oxide hydrate, rusty steel natural reaction is the formation process of the original ore. The reaction of this corrosion process can be used to calculate the thermodynamic Gibbs free energy criterion thermodynamic described.