Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers


General Corrosion

Last updated: August 31, 2017

What Does General Corrosion Mean?

General corrosion is a type of corrosion that takes place at almost the same rate on the surface of the entire metal that is exposed to the corrosion-causing conditions. The surface that results from the corrosion process can have areas where there is either more or less penetration. In such cases, several minimum penetrations can lead to a maximum penetration. As a result of these, the corroded surfaces have a mottled appearance.

General corrosion is also known as uniform corrosion or general attack corrosion.


Corrosionpedia Explains General Corrosion

General corrosion is normally characterized by an attack that appears to be uniform in nature. The uniformity is normally spread on the whole surface of the metal, resulting in a smooth appearance. The attack that leads to corrosion on the surface of the metal is the result of the material being subjected or exposed to a medium that is corrosive in nature. For this reason, the corrosion rate is therefore defined as the loss of mass per unit of surface area. In other words, the corrosion rate can be expressed as mean loss of metal per unit over time, or units of mm per year.

Alkaline solutions and strong acids create an environment where general corrosion is most likely to occur on stainless steel. The factors leading to corrosion can either be increased or reduced depending on the addition of reducing or oxidizing components. With different additives, there can be a great variance in the performance of the steel, depending on the additives used. Due to this reason, it is crucial to consider the characteristics of the environment where certain material is to be used.

In many cases, general corrosion is objectionable only from an appearance standpoint. It can add color and appeal 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.

Estimation of life cycle cost can be one of the effective ways of utilizing the economic advantage that comes with corrosion resistance. Corrosion coupons are important tools that are utilized when determining the wall thickness for the life of particular equipment.

While general corrosion may represent only a small fraction of industrial corrosion failures, the total tonnage wasted is generally regarded as the highest of all forms.



General Attack Corrosion

Uniform Surface Corrosion

Uniform Corrosion

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