Corrosion – Erosion

Damage to the surface of materials due to the synergic action of the corrosion-erosion has received significant attention among researchers due to the severity of the problems caused by this phenomenon on the service components. The erosion problems are associated with corrosion problems if the collision between the particles and the material takes place in a moist environment, creating a synergy that translates into an increase of the overall damage speed. The synergy between the two damage mechanisms produces a total damage on the generally upper material of the sum of the rate of damage due to erosion pure or pure corrosion.

Corrosion-erosion on stainless stell tube

The interactions of these two processes are extremely complex nature and emerges the need to conduct a careful characterization of the material both in terms of resistance to erosion and corrosion, as well as the synergistic effect evaluation in order to choose the most suitable material for a given environment. Generally it describes the synergy as the difference between the damage due to the combined action of erosion-corrosion and the sum of the damage linked to only contributions linked to erosion and pure to pure corrosion. The study of phenomena of erosion by particles immersed in aqueous environments has progressed significantly in recent years. The complexity of the process of corrosion-erosion is mainly due to the multiplicity of causes that can promote it. It is possible, in principle, identify common causes for both erosion phenomena that corrosion-erosion, or rather, indicate the erosion as a special case of corrosion-erosion, in which the contribution to the damage linked to the corrosion can be considered negligible. The associated damage to the corrosion-erosion phenomena depends on several parameters involving the test material (hardness, resilience, of alloying content, modulus of elasticity, microstructure, any heat treatment), the particles dispersed in the fluid (speed, size, shape, , density, angle of impact, hardness, impact strength and modulus of elasticity), the flow conditions (speed, flow regime) and the test fluid in which are dispersed the particles (pH, corrosion potential of the material in the environment , the presence of chlorides, viscosity, pressure, temperature). The effects of variables on the damage mechanism are still poorly known today, also as regards the metallic materials. What is currently well known is that there are positive and negative interactions between the process of corrosion and erosion. Erosion may, in fact, promote corrosion due to the removal of the surface film liabilities (contribution of additive type), however, the corrosion can inhibit erosion, in the sense that a particularly stable and ductile film can absorb effectively the shock. Recently, several works for the construction of the erosion corrosion maps in order to isolate and understand the effects of different variables on the damage and understand more fully the damage mechanism were conducted.

Corrosion – erosion process on stainless steel

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