Types of corrosion in heat exchanger
Metal corrosion refers to the chemical or electrochemical action of the surrounding medium, and the destruction of the metal under the action of physical, mechanical or biological factors, that is, the metal produced damage under the action of its environment.The common types of metal corrosion in plate heat exchangers are as follows:
(1)Uniform Corrosion: A macroscopically uniform corrosion failure that occurs over the entire surface exposed to the medium, or over a large area, which is called uniform corrosion.
(2)Crevice Corrosion: Severe crevice corrosion occurs in the gaps and covered areas of the metal surface.
(3)Contact Corrosion: Two metals or alloys with different potentials are in contact with each other and immersed in the electrolyte solubilizing solution. There is a current passing between them, the metal corrosion rate of the positive potential is reduced, and the metal corrosion rate of the negative potential is increased.
(4)Erosion Corrosion: Corrosion is a corrosion that accelerates the corrosion process due to the relative motion between the medium and the metal surface.
(5)Selective Corrosion: A phenomenon in which an element of an alloy preferentially enters the medium due to corrosion is called selective corrosion.
(6)Pitting Corrosion:Concentration on a small spot on a small metal surface is called pitting corrosion, or pitting corrosion.
(7)Intergranular Corrosion: Intergranular corrosion is a corrosion that preferentially corrodes the grain boundary of a metal or alloy and the vicinity of the grain boundary, while the grain itself is less corroded.
(8)Hydrogen destruction:Metals in the electrolyte solution can cause damage due to hydrogen permeation due to corrosion, pickling, cathodic protection or electroplating.
(9)Stress corrosion cracking (SCC) and corrosion fatigue are material fractures caused by the combined action of corrosion and tensile stress in a certain metal-medium system.