TITLE:HOW CORROSION OCCURS IN INDUSTRY AND METHOD TO PREVENT IT.
DESCRIPTION:
v INDUSTRYAL CORROSION:
Corrosion is when a refined metal is naturally converted to a more stable form such as its oxide, hydroxide or sulphide state thisleads to deterioration of the material.
Corrosion is when a refined metal is naturally converted to a more stable form such as its oxide, hydroxide or sulphidestate this leads to deterioration of the material.
· Most oberved corrosion type in industry
1)Uniform Corrosion
2)Pitting Corrosion
3)Crevice Corrosion
4)Intergranular Corrosion
5 Different Types of Corrosion Prevention Methods
· BARRIER COATINGS. One of the easiest and cheapest ways to prevent corrosion is to use barrier coatings like paint,...
· HOT-DIP GALVANIZATION. This corrosion prevention method involves dipping steel into molten zinc. The iron in the...
· ALLOYED STEEL (STAINLESS). Alloyed steel is one of the most effective corrosion prevention methods around, combining...
· CATHODIC PROTECTION. Cathodic protection protects by electrochemical means. To prevent corrosion, the active...
OUTCOMES:
Uniform Corrosion
Uniform corrosion is characterized by corrosive attack roceeding evenly over the entire surface area, or a large fraction of the total area. General thinning takes place until failure. On the basis of tonnage wasted, this is the most important form of corrosion.
However, uniform corrosion is relatively easily measured and predicted, making disastrous failures relatively rare. In many cases, it is objectionable only from an appearance standpoint. As corrosion occurs uniformly over the entire surface of the metal component, it can be practically led control by cathodic protection, use of coatings or paints, or simply by specifying a corrosion allowance. In other cases uniform corrosion adds color and appeal to to a surface. Two classics in this respect are the patina created by naturally tarnishing copper roofs and the rust hues produced on weathering steels.
The breakdown of protective coating systems on structures often leads to this form of corrosion. Dulling of a bright or polished surface, etching by acid cleaners, or oxidation (discoloration) of steel are examples of surface corrosion. Corrosion ant resist alloys and stainless steels can become tarnished or oxidized in corrosive environments. Surface corrosion can indicate a breakdown in the protective coating system, however, and should be examined closely for more advanced attack. If surface corrosion is permitted to continue, the surface may become rough and surface corrosion can lead to more serious types of corrosion.
Pitting Corrosion
Pitting corrosion, or pitting, is a form of extremely localized corrosion that leads to the creation of small holes in the metal. The driving power for pitting corrosion is the depassivation of a small area, which becomes anodic (oxidation reaction) while an unknown but potentially vast area becomes cathodic (reduction reaction), leading very localized galvanic corrosion. The corrosion penetrates the mass of the metal, with a limited diffusion of ions.
Severe pitting corrosion problems caused by chloride ions on a truss beam of the Nandu River Iron Bridge (Hainan Province, China) leading to the complete rupture of a metallic element.
Another term arises, pitting factor, which is defined as the ratio of the depth of the deepest pit (resulting due to corrosion) to the average penetration, which can be calculated based on the weight loss.
Crevice Corrosion
Crevice corrosion refers to corrosion occurring in confined spaces to which the access of the working fluid from the environment is limited. These spaces are generally called crevices. Examples of crevices are gaps and contact areas between parts, under gaskets or seals, inside cracks and seams, spaces filled with deposits and under sludge piles.
Intergranular
Corrosion
Intergranular corrosion (IGC), also known as intergranular attack (IGA), is a form of corrosion where the boundaries of crystallites of the material are more susceptible to corrosion than their insides. (Cf. transgranular corrosion.)
1. BARRIER COATINGS
One of the easiest and cheapest ways to prevent corrosion is to use barrier coatings like paint, plastic, or powder. Powders, including epoxy, nylon, and urethane, adhere to the metal surface to create a thin film. Plastic and waxes are often sprayed onto metal surfaces. Paint acts as a coating to protect the metal surface from the electrochemical charge that comes from corrosive compounds. Today’s paint systems are a combination of different paint layers that serve different functions. The primer coat acts as an inhibitor, the intermediate coat adds to the paint’s overall thickness, and the finish coat provides resistance to environmental factors.
The biggest drawback with coatings is that they often need to be stripped and reapplied. Coatings that aren’t applied properly can quickly fail and lead to increased levels of corrosion. Coatings contain volatile organic compounds, which make them hazardous to people and the environment.
Failing Barrier Coating
2. HOT-DIP GALVANIZATION
This corrosion prevention method involves dipping steel into molten zinc. The iron in the steel reacts with the zinc to create a tightly bonded alloy coating which serves as protection. The process has been around for more than 250 years and has been used for corrosion protection of things like artistic sculptures and playground equipment.
Unfortunately, galvanization can’t be done on-site, meaning companies must pull equipment out of work to be treated. Some equipment may simply be too large for the process, forcing companies to abandon the idea altogether. In addition, zinc can chip or peel. And high exposure to environmental elements can speed up the process of zinc wear, leading to increased maintenance. Lastly, the zinc fumes that release from the galvanizing process are highly toxic.
3. ALLOYED STEEL (STAINLESS)
Alloyed steel is one of the most effective corrosion prevention methods around, combining the properties of various metals to provide added strength and resistance to the resulting product. Corrosion-resistant nickel, for example, combined with oxidation-resistant chromium results in an alloy that can be used in oxidized and reduced chemical environments. Different alloys provide resistance to different conditions, giving companies greater flexibility.
Despite its effectiveness, alloyed steel is very expensive.
4. CATHODIC PROTECTION
Cathodic protection protects by electrochemical means. To prevent corrosion, the active sites on the metal surface are converted to passive sites by providing electrons from another source, typically with galvanic anodes attached on or near the surface. Metals used for anodes include aluminum, magnesium, or zinc.
While cathodic protection is highly effective, anodes get used up and need to be checked and/or replaced often which can drive up costs of maintenance. They also increase the weight of the attached structure and aren’t always effective in high-resistivity environments.
5. EONCOAT – A NEW WAY TO PROTECT ASSETS FROM CORROSION
Choosing the right corrosion prevention for your equipment isn’t easy. Each of the above methods has its pros and cons. EonCoat is a cost-effective, maintenance-free, and easily applied solution which protects the life of the asset. It works by a combination of the above methods. First, it alloys the metal, then provides a thick layer of inhibitors that will repair any damage to the alloy layer. EonCoat uses no toxic chemicals and has no VOC’s so it is the most environmentally friendly solution. Independent testing shows this solution to be the most effective and long-lasting of all the alternatives. The 30-year warranty ensures your equipment stays protected. To Learn More about EonCoat download our
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