As mentioned in other posts, the metals corrosion is a real chemical reactions. Briefly, they are phenomena that cause slow material deterioration in contact with the external environment. Today we will talk specifically about metal dusting corrosion.
What is metal dusting corrosion?
These corrosion can stand out in the dry corrosion (at high temperatures and in the absence of condensed water) and in metal dusting corrosion. The latter, therefore, occurs in the presence of condensed water. Metal dusting corrosion is an electrochemical phenomenon, but how does it work? Through both:
- anodic reaction of the metal (Me = Mez+ + ze)
- cathodic reaction that change depending on the environment
- discharge reaction of hydrogen
- reduction of atmospheric oxygen.
Therefore, the presence of an electrolyte is fundamental, such as a layer of condensed moisture on the metal surface with ions. Why?
For the presence of:
- gases dissolved
- contaminated salts on the surface.
What type of damage does it cause?
Usually the damages caused by metal dusting corrosion are really relevant. These can be split into:
- direct damages (replacing parts or structures)
- loss of product
- maintenance and recovery
- redundancy of equipment
- project and insurance charges
- indirect damages (loss of production for different causes)
- blocked plants
- limited productivity
- environmental rehabilitation later than products spreading
- reduction in service life of plants/structures
How to prevent metal dusting corrosion?
So the question arises: how can we prevent metal dusting corrosion? This problem can be solved with a little foresight.
- design carefully, avoiding the presence of
- interstices
- water/moisture cavity
- valve vents
- mechanical/thermal stresses
- correctly choosing the material (especially based on the aggressiveness of the environment)
- choosing the active and passive security methods (which reduces the speed of the electrochemical reactions through specific actions or special barriers)
- performing periodic maintenance (thanks to direct observation and other methods).
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