A guide to corrosion prevention - how corrosion can occur, its consequences and how to prevent it.
What is corrosion?
Corrosion occurs when a material decays due to environmental influences. Corrosion is a natural process that occurs when three conditions are met: the presence of moisture, a metal surface, and an oxidant (also called an electron acceptor).
As a result of the process, the metal is converted into one of its salts, i.e. oxides / hydroxides / sulfides, depending on the material. Metal is chemically unstable and its salt is more stable. One of the most common forms of corrosion is corrosion. When iron rusts, the reddish fluffy substance that is the result of the corrosive process is iron oxide.
Effects on metal
Corrosion affects metals in many ways. When metal structures corrode, their integrity is impaired and they become more prone to collapse. Once corrosion occurs, it can expand rapidly, making it necessary to be careful and prevent it from starting.
Corrosion Prevention Methods
The following methods are commonly used to prevent corrosion:
1. Choice of metal used
A simple measure to prevent corrosion is to use corrosion resistant metal. Aluminum and stainless steel are typical examples of such metals.
2. Protective coating
A cost effective method of preventing corrosion is to apply a coat of paint. Paint acts as a barrier between metals and elements, preventing the flow of electrochemical charge that causes corrosion.
Powder coatings are also a cost-effective anti-corrosion solution. Dry powder is used to coat the metal surface. Afterwards, the metal is heated, causing the powder to merge with the metal in a homogeneous, uniform sheath. The various powder formulations used are polyester, nylon, urethane, epoxy and acrylic.
3. Control of environmental conditions
Corrosion is the result of a chemical reaction between metals and certain gases present in the environment. If the presence of these gases can be controlled in the environment, then the reaction can also be controlled. Simple measures in this regard reduce exposure to rain or atmospheric humidity. Complex measures would be to control the sulfur / oxygen / chlorine content of the environment.
An example of a complex measure is the treatment of water present in boilers using a softener. Softeners remove calcium and magnesium in water, which are highly reactive metals that increase the potential for corrosion. In addition, softeners also help to manage oxygen content and alkalinity of water.
Corrosion prevention can be achieved by coating the metal surface with other metal that has a relatively higher or lower oxidation potential.
There are two types of electroplating: anode protection and cathodic protection
5. Anode protection
For anode protection, the surface to be protected is coated with a metal that is less reactive (eg tin). Using the example given, the tin is far less susceptible to corrosion, so that the surface to which it is applied will be safe as long as there is a coating. The reason why this protection is called anode is that in the process, the metal surface that wants to be protected becomes anode.
Anodic protection serves to protect carbon steel tanks used to store fifty percent of caustic soda and sulfuric acid. Cathodic protection cannot be used in such an environment as the current requirements for it would be extremely high.
6. Cathodic protection
Applying a zinc layer to the surface of iron alloy steel is a common example of cathodic protection. This process is also called galvanizing. Because zinc is more reactive than steel, it will corrode. Oxidation will prevent corrosion of the steel. The reason for calling this protection cathodic is that in the process, the metal surface to be protected becomes a cathode.
Cathodic shielding is often used to protect steel pipelines that carry fuel or water, ship hulls, boilers and offshore oil platforms.
7. Design modification
A passive measure of corrosion prevention is to design the structure in a way that prevents corrosion and, as a result, increases the longevity and durability of all corrosion coatings. Ideally speaking, designs should be such as to prevent water and dust from being trapped, facilitate the flow of air currents and avoid cracks. Finally, the design should ensure that the structure in question is regularly maintained.
8. Corrosion inhibitors
Another way to prevent corrosion is to use a corrosion inhibitor. These are chemicals that react with either a metal surface or with gases in the environment to "inhibit" the chemical reactions that cause corrosion. Inhibitors are used to coat the metal surface in a protective film. There are two forms in which inhibitory chemicals can be applied. They can be mixed with a suitable solvent; the resulting solution is subsequently applied. Or, using conventional dispersion techniques, they can be applied as a protective layer. The process of applying a corrosion inhibitor is called passivation.
In this process, a protective material (usually some kind of metal oxide) is used to form a layer over the metal surface. This layer is what barricades the surface from corrosion. Factors affecting the applied layer include ambient temperature, environmental pH, and the chemical composition of the surrounding atmosphere. One additional advantage of this process is that a patina is gradually formed on the applied layer. As a result, the structure becomes more beautiful over time. This is something that can be seen on roofs that have copper panels. Another example of the process of passivation is the color of the Statue of Liberty. The patina, which is blue-green in color, has evolved over a structure that acts as a barrier to the corrosion of copper below. Corrosion inhibitors are commonly used in chemical, oil refineries and water treatment plants.
An immediate step you can take is to use the WD-40 multifunctional product. The spray is capable of protecting metal parts for a specified period if exposed to the environment and possibly longer if the object is indoors. It is recommended to apply WD-40 regularly.