Effectsof corrosion.There are multiple consequences of corrosion thatexist and many times the effects of corrosion is more severe and devastatingthat simple material losses. In many cases due to corrosion many of the partshave to be replaced even if there is a small amount of metal corroded away, itis because of this that many companies spend a huge amount of money on theprevention of corrosion and the replacement of such parts; the annual amount ofmoney that is spent in order to battle the effects of corrosion is more that$276 billion in the US alone.
The effects of corrosion are as listed:· Reduction in thematerials thickness that can result in reduction of mechanical strength and ifnot taken care of it will result in failure.· Loss of life orinjuries that may arise in case there is a serious structural failure.· For goods thatare sold for cosmetic purposes, corrosion can cause their appearance todeteriorate resulting in reduction of price at which they are sold.· Loss of time asthe machinery is repaired and cannot be used in that specific time.· Damage to valves,pumps, etc. as small metal particles move through them causing them to corrodefrom the inside· There is an addedcomplexity in designing the machinery, as it has to be designed so that thereis minimum amount of corrosion and so that parts could be easily replaced.For the case of properties of the metal corrosion can:· Decrease inthickness results in decreased strength.· Reducedductility.
· Reducedtoughness.CorrosionpreventionAs for the effects of corrosion, corrosion preventiontechniques are applied in order to minimize the effects of carrion so that thepart could be used for a longer duration of time. Methods for prevention ofcorrosion are classified into the following categories.· Modification ofmaterials.· Change ofenvironment.· Electrochemicaltechniques.
· Barrier films.· Change of design.Modification of materialCorrosion can be controlled by complete or partialchange in the material used. Modification can be done by using one of the twoways.· Coating the metalwith a corrosion resistant coating, which can be either another metal,protective coating, derived from the metal itself, coating it with an organiccoating.· Alloying themetal to produce a corrosion resistant alloy such as stainless steel.
Alteration of environment· Removal of oxygen.· Addition ofinhibitors (cathodic, anodic, mixed inhibitors).· Make the fluidpassing through pipes be at lower temperature and velocity.· Dehumidification.· Alkalineconditioning.Electrochemical techniquesAs corrosion is an electrochemical process, thereforethe rate at which it occurs could be controlled by passing an anodic orcathodic current. One of the following methods can do this:· Sacrificialanodic protection.· Impressed currentcathode protection.· Sacrificialcoating.Barrier filmsBarrier films are protective coatings that isolate themetal from the corrosive environment; this protective coating doesnot provideany mechanical properties to the material however, for long time use barrierfilms provide the best protection under severe chemical conditions.Some barrier films/Coverings are given below;Coating/Covering· Electroplating· Electro lessplating· Zinc coatings· Anodizing· Chromate filmingDesign of structureBy changing the design of the structure we can minimizethe amount of corrosion that takes place, design measures include:· Avoid sharpcorners.· Complete drainageof vessels.· No waterretention in any part of the device.· Avoid contactbetween different metals.· Easy replacementof venerable parts.· Avoid excessmechanical stress.http://www.drillingformulas.com/important-mechanical-properties-of-materials-and-effect-of-corrosion-on-load-carrying-components/https://www.linkedin.com/pulse/materials-effects-economic-impact-corrosion-mohammad-abolghasemihttp://www.wermac.org/materials/corrosion.htmlhttp://www.sciencedirect.com/science/article/pii/S0301679X02000555https://www.scientific.net/MSF.202/book