pitting and crevice corrosion

Throughout the history of industrial sciences, two distinct types of corrosion have emerged – pitting corrosion and crevice corrosion. Generally speaking, pitting corrosion is the result of anodic accumulation of corrosion in small pores, pockets or sections of a given material. By contrast, crevice corrosion occurs when there is a lack of adequate ventilation from oxygen-rich air or from insufficient liquid volumes.

Pitting corrosion affects all types of metals, though it is most prevalent in steel. This form of corrosion is often the result of highly chlorinated water, and it is most common when the pH level of the water is below 3.5. Pitting can occur when a given material is subjected to chlorides, sulfates, and nitrates, though a number of other factors can also contribute to its development. This form of corrosion is often characterized by small pits and perforations that can weaken the overall structural integrity of a given material.

To reduce the likelihood of pitting corrosion, it is important to reduce the amount of chlorides and other ionic species that are present in the environment. A proper electrochemical balance can also help to prevent its onset. Likewise, proper maintenance and inspection of material components helps to ensure that any existing defects or weaknesses are caught and mitigated in a timely manner. Another important factor is the use of protective coatings on the material, as this can help to reduce the likelihood of corrosion.

By contrast, crevice corrosion is most commonly found in stainless steel components. It occurs when the surface is shielded from oxygen by a restricitive seal or other material component. As a result of the lack of oxygen, the stainless steel component is unable to develop its natural protective oxide layer, which makes it more susceptible to corrosion. This form of corrosion is often a result of inadequate maintenance, which is why regular inspection and upkeep are essential to prevent its onset.

To reduce the likelihood of crevice corrosion, it is important to ensure that the surface is exposed to adequate air flow. Likewise, periodic cleaning is essential to remove any build up of contaminants that could eventually lead to corrosion. Additionally, protective coatings and stainless steel components should be considered for components that are most vulnerable to this type of corrosion.

Overall, the prevention of pitting and crevice corrosion lies in proper maintenance and the application of appropriate protective coatings. If the proper care is taken to ensure the material components are exposed to a balanced environment and are regularly inspected, the likelihood of corrosion forming can be minimized.

Erosion by dissolution and cracking is a natural process that can gradually wear away rocks, soil and manmade materials. When water dissolves minerals, it can break down rocks and sediment. This is known as chemical erosion. When water freezes and the ice expands, it can cause cracks in rocks and other materials, leading to physical erosion.

Dissolution erosion happens when something is exposed to air or water, which causes it to deteriorate or break down. Its a slow process, and it can cause a variety of things, including changes in the surface of rocks, changes in the composition of substances, and the creation of new geological features. Its particularly noticeable with sedimentary rocks, which are composed of materials that were once at the surface but were dissolved and moved away over time.

Cracking erosion is the process when water is individually forced into crevices and joints in rocks or along the edges of fractures. Its the same type of erosion that happens when water gets under the edges of sidewalks and breaks them apart. This type of erosion intensifies in areas that experience alternating freezing and thawing.

Both chemical erosion by dissolution and physical erosion by cracking can be detrimental to manmade structures and have a large-scale effect on the environment. In extremely dry areas, dissolution erosion can cause a lot of damage to rocks and soil, which can lead to floods in the affected areas when heavy rains occur. Cracking erosion can damage foundations and roads, while also altering the flow of rivers and streams. To reduce erosion, structures built near rivers and streams should have a sloping surface that encourages water to run off rather than seep in. In dryer regions, slow-release irrigation systems, rock mulch and plant cover can help reduce erosion.

In conclusion, erosion by dissolution and cracking can be both detrimental to manmade structures and have an overall impact on the environment. To prevent both types of erosion, the proper materials and methods should be used when constructing anything in an area prone to erosion.