The gradual destruction of material, usually metals, due to chemical reaction with its environment. In an electrochemical reaction metals will get corrode resulting in metal loss as oxidation at the anode side and plating out of the metals at the cathode side. According to chemical engineers in an industry two types of corrosion happens to the metals with its interaction with electro chemical reaction they are general corrosion and localized corrosion.
The slow degradation of materials with the interaction of chemical and due to electro chemical reaction is known as generalized corrosion. In generalized corrosion there is a uniform loss of metal thickness. This degradation is usually measured by the loss of thickness and corrosion rate per year.
Localized corrosion usually confined to one area of at the area near to the joints of the metals or pipes fittings hence the name. Localized corrosion usually classified into three types they are pitting corrosion, inter granular corrosion and crevice corrosion. The most damaging form of corrosion pitting corrosion is usually the corrosion of metals surface at the confined point or small surface. This type of corrosion usually takes place in the form of cavities. Inter granular type of corrosion requires a microscopic investigation and is the result tress. Inter granular corrosion is also known as Inter crystalline corrosion or inter centric corrosion. As the name suggests this type of corrosion usually takes place between grains or crystals. In Industrial terminology this corrosion is generally known as "inter granular stress corrosion cracking (IGSCC)". When the metal is corrosion resistant but the joints between the metals is ignored the most common corrosion is crevice corrosion. This corrosion is a result of localized attack on a metal surface at the gap or crevice between two joining areas.
Discovered by Roy Plunk a research chemist at DuPont, Fluoropolymers are sell under the brand name Teflon by DuPont. Fluoropolymers has the ability to withstand chemical reactions at high temperature. Fluoropolymers are capable of withstanding chemical reaction at up to 260 Celsius. Fluoropolymers are selected on the basis of established criteria of required life, mean time between inspection, ease of fabrication, frequency of inspection, extent of maintenance and fabrication cost.
The end user often makes the decision based on the initial cost rather than the life cycle of the equipment however the decision should be made according to the life of the equipment.
Corrosion of Polymers:
The chemical structure of polymers makes it the most suitable candidate in the industry for applying it in preventing the corrosion of metals. The Polymers don’t get corrode easily by electro chemical reaction and processes. In the corrosion following descriptions are used cracking, blistering, chalking, swelling, discoloration. The metals in the industry gets corrode after experiencing electro chemical reaction at a specific rate but this is not the case in case of Polymers. Polymers don’t corrode easily or gets corrode rather very slowly.
About Selection of Polymers:
Fluoropolymers are fundamental to many metallic and non metallic materials in industrial and non industrial uses. The Selection of Fluoropolymers like any other component or material is usually degradation mechanism, its rate and criteria based on the expected life of the unit. The ability to fabricate the Fluoropolymers in the required shape is another consideration in its selection.