Corrosion is a natural phenomenon that occurs in metals, except gold and platinum, other known metals undergo a corrosive effect when placed in contact with atmospheres containing oxygen or hydrogen, which is why we need to know live with corrosion, for this we must know the methods and techniques that provide and delay the presence of this natural phenomenon.
Mainly we can protect metals from corrosion by taking action in the phases of design, modifying the environment or medium in which the piece or structure will be exposed, applying coatings to protect the piece or by anodic or cathodic protection.
Modifying the environment
Protection coatings (metallic and organic)
Anodic and cathodic protection
During the design phase, the designer must keep in mind the parameters that can cause corrosion on the piece or structure that is being designed, will not help all the time spent on calculations of resistance if the selected material corrodes rapidly in the environment in which will be exposed.
Following there are some parameters or guides that the designer has to consider:
Selection of materials according to the environment in which the piece or structure will be exposed, for example not use aluminum in alkaline environments.
Prevent joint design of different materials in the galvanic series that can produce galvanic corrosion.
Know the parameters which will be exposed the structure, parameters such as the nominal, minimum and maximum temperature, pressure and flow rate, the chemical composition of the compounds which will be exposed...
Avoid crevices and areas where can accumulate solid, liquid or gaseous materials, define drainage in the designs.
In the event that the selected material need some type of coating which prevents corrosion, the piece has to be designed in such a way that does not contain parts or inaccessible areas as well as sharp corners or edge.
Definition of corrosion tolerances as well as maintenance and inspection requirements.
The modification of the environment consist to reduce or eliminate the corrosive agents which is under the part or structure to be protected.
Basically it is used corrosion inhibitors, sequestrants and pH modifiers as techniques or methods to modify the environment.
For the use of these techniques is essential to know exactly the type of corrosive agent which will always be under the piece or the structure.
Protection by coatings
In this type of technique which is intended to isolate the piece or structure of the corrosive environment by applying an organic or metallic coating that makes the barrier function between the environment and the metal.
There are basically 2 types of coatings that can apply as techniques of corrosion protection:
Organic coatings - mainly refer to organic compounds such as paints, plastics and adhesives. Also included protective organic layer created by applying plasma on certain substrates.
Metallic coatings - refer to the set of techniques covering the substrate with a protective metal layer and firmly attached, techniques such as galvanizing, anodizing, metal spraying hot, metal electrodeposition...
Anodic and cathodic protecction
These types of protection are based onelectrochemical corrosion phenomenon to control the speed and progress of corrosion.
In cathodic protection make the piece or structure to be protected act as cathode; so that there not occurs corrosion, for this we can use some of these techniques:
Cathodic protection by impressed current.
Cathodic protection by sacrificial anodes.
In anodic protection make the piece or structure to be protected act as anode, causing it to corrode slowly and go to a state of passivity, this technique is restricted only to materials that possess an active-passive behavior.
Of all the methods mentioned above, the paint is the most commonly used to protect pieces or structures against corrosion, mainly due to low cost that requires and the extra functionality of aesthetic and design that brings the paints.
If you like, share it