How is pitting corrosion formed?
What Causes Pitting Corrosion? Pitting corrosion occurs when the cathode (damaged coating) is large and the anode (exposed metal) is small.
Typically the surface protection layer or film becomes the cathode when it is damaged and cracked.
A small area of metal is then exposed and becomes the anodic..
What are the factors of pitting corrosion?
Another term arises, pitting factor, which is defined as the ratio of the depth of the deepest pit (resulting due to corrosion) to the average penetration, which can be calculated based on the weight loss..
What are the shapes of pitting corrosion?
Pitting corrosion occurs in various shapes.
They can be small, large, circular, hexagonal or irregular shaped.
Puts usually grow downward in the direction of gravity and most pits form on top of a horizontal surface..
What causes corrosion pitting?
Most cases of pitting are believed to be caused by local cathodic sites in an otherwise normal surface.
Apart from the localized loss of thickness, corrosion pits can also be harmful by acting as stress risers.
Fatigue and stress corrosion cracking may initiate at the base of corrosion pits..
What is pitting corrosion?
Pitting corrosion is a localized form of corrosion by which cavities or "holes" are produced in the material.
Pitting is considered to be more dangerous than uniform corrosion damage because it is more difficult to detect, predict and design against.
Corrosion products often cover the pits..
What is the difference between pitting and crevice corrosion?
Similar to pitting corrosion, crevice corrosion is initiated with the breakdown of stainless steel's protective oxide film and continues with the formation of shallow pits.
However, rather than occurring in plain sight, crevice corrosion—as its name implies—occurs in crevices..
What is the mechanism for pitting corrosion?
Pitting Corrosion Mechanism
In the mechanism of pitting corrosion, the oxidation of the metal occurs, resulting in an acidity which is localised.
The generous separation of the cathodic half-reaction and the anodic half-reaction helps maintain this localised acidity..
What is the mechanism of pitting corrosion?
Pitting Corrosion Mechanism
In the mechanism of pitting corrosion, the oxidation of the metal occurs, resulting in an acidity which is localised.
The generous separation of the cathodic half-reaction and the anodic half-reaction helps maintain this localised acidity..
What is the pitting potential of corrosion?
Pitting potential refers to the least positive current and voltage at which pits develop or grow on a metallic surface.
This is the electrochemical potential in a given environment above which a corrosion pit initiates on a metallic surface..
- By statistical analysis of hundreds of individual pits, three stages of pitting corrosion, namely, induction, propagation, and saturation, are quantitatively distinguished.
- Pitting corrosion occurs when localised areas of steel lose their protective layer.
This area becomes anodic, while part of the remaining metal becomes cathodic, producing a localised galvanic reaction. - Pitting Corrosion
This occurs when the material of the metal pipe is slowly worn away over time, but the wear is not uniform across the pipe.
Instead, small holes or pits are created.
This type of corrosion can be extremely difficult to detect because the damage is not often known until the pipe starts leaking.
