Type of Corrosion
Types of Corrosion
1. Discuss the major types of corrosion.
Uniform Corrosion:
Uniform corrosion is characterized by corrosive attack proceeding 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. (corrosion-doctors.org) This reminds me of some of the contractor spec’s I have seen for just this type of corrosion. Many of the clarification mechanisms I have seen specs for require a safety factor that if a 1/4” of the total cross section of each member were to corrode away that the mechanism would still be strong enough to take the load. These mechanisms are usual in a very acidic, completely submerged environment, so this would make a lot of sense for a long salting system.
Erosion Corrosion:
Erosion corrosion is acceleration in the rate of corrosion attack in metal due to the relative motion of a corrosive fluid and a metal surface. The increased turbulence caused by pitting on the internal surfaces of a tube can result in rapidly increasing erosion rates and eventually a leak. (corrosion-doctors.org) An example would be water running over a dam, usually a movable gate. Another example would be an impeller in a clarification tank for mining purposes. I have experience with these and the motion of the spinning impeller is the most damaging. I have seen the corrosion patterns in the metal from is spinning and turbulence.
Galvanic Corrosion:
Galvanic corrosion (also called ' dissimilar metal corrosion ' or wrongly 'electrolysis ') refers to corrosion damage induced when two dissimilar materials are coupled in a corrosive electrolyte. (corrosion-doctors.org) I have seen this in aluminum hand rails for walkway bridges. Usually this happens when a contractor forgets to put the rubber spacer between the aluminum and steel. The aluminum last only about a year before the hand rail falls off, making for a hug problem.
1. Discuss the major types of corrosion.
Uniform Corrosion:
Uniform corrosion is characterized by corrosive attack proceeding 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. (corrosion-doctors.org) This reminds me of some of the contractor spec’s I have seen for just this type of corrosion. Many of the clarification mechanisms I have seen specs for require a safety factor that if a 1/4” of the total cross section of each member were to corrode away that the mechanism would still be strong enough to take the load. These mechanisms are usual in a very acidic, completely submerged environment, so this would make a lot of sense for a long salting system.
Erosion Corrosion:
Erosion corrosion is acceleration in the rate of corrosion attack in metal due to the relative motion of a corrosive fluid and a metal surface. The increased turbulence caused by pitting on the internal surfaces of a tube can result in rapidly increasing erosion rates and eventually a leak. (corrosion-doctors.org) An example would be water running over a dam, usually a movable gate. Another example would be an impeller in a clarification tank for mining purposes. I have experience with these and the motion of the spinning impeller is the most damaging. I have seen the corrosion patterns in the metal from is spinning and turbulence.
Galvanic Corrosion:
Galvanic corrosion (also called ' dissimilar metal corrosion ' or wrongly 'electrolysis ') refers to corrosion damage induced when two dissimilar materials are coupled in a corrosive electrolyte. (corrosion-doctors.org) I have seen this in aluminum hand rails for walkway bridges. Usually this happens when a contractor forgets to put the rubber spacer between the aluminum and steel. The aluminum last only about a year before the hand rail falls off, making for a hug problem.
References: .besg.group.shef.ac.uk/Research_Area/Applied_Biofilm/Biocorrosion.htm. (n.d.). astm.org. (n.d.). cdcorrosion.com. (n.d.). corrosion.ksc.nasa.gov. (n.d.). corrosion.ksc.nasa.gov/filicor.htm. (n.d.). corrosion-doctors.org. (n.d.). http://en.wikipedia.org/wiki/Hydrogen_damage#Blistering. (n.d.).