1.What is the physical separation between the electrolysis reaction and the bubbles?
This is the core physical process of electrolytic cleaning. After the strip steel enters the electrolytic cell, it becomes an electrode (cathode or anode) through a conductive roller. Under the action of current, the electrolyte solution (usually an alkaline solution) on its surface undergoes electrolysis, generating a large number of tiny bubbles.
Function: These bubbles (especially the hydrogen bubbles generated on the cathode side, which are more numerous and smaller in size) are generated violently on the strip surface and rise rapidly to escape. This violent bubble precipitation and movement will have a strong tearing, peeling and scouring effect on the oil film and solid particles on the strip surface, and can "push" off stubborn dirt (such as saponification reaction residues and fine iron powder) that is difficult to remove by ordinary alkaline washing and is embedded in the surface micropores.
2.What are saponification, emulsification, and dispersing?
Saponification: The rolling oil on the strip surface is mostly mineral oil or animal/vegetable oil. The alkali in the electrolyte (such as NaOH, KOH) reacts chemically with the animal/vegetable oil to produce water-soluble soap and glycerin, thus removing the oil from the surface.
Emulsification and Dispersion: For mineral oils that are difficult to saponify, the surfactant in the electrolyte emulsifies them, causing them to detach from the strip surface and disperse in the solution. Simultaneously, the dispersant in the solution prevents the detached contaminants (such as iron powder) from re-adhering to the strip surface.
3.What is electrochemical desorption?
There is usually an electrostatic attraction between the steel strip surface and oil and particles. During electrolysis, the charge state of the steel strip surface changes drastically, which disrupts these attraction forces, making it easier for oil and particles to desorb from the steel strip surface and enter the solution.
4.What is the process of electrolytic cleaning?
Immersion and Wetting: The steel strip is immersed in the alkaline solution, where the oil and dirt begin to soften and emulsify.
Electrolytic Explosion: Upon application of electricity, numerous tiny bubbles are generated on the surface of the steel strip. These bubbles explode and peel away stubborn dirt.
Chemical Dissolution: The alkaline solution reacts with residual grease through saponification, dissolving it.
Physical Rinsing: The high-speed flowing electrolyte and rising bubbles carry away the detached dirt.
Water Washing: After electrolytic cleaning, hot water washing and rinsing with clean water are usually performed immediately to thoroughly remove any remaining alkaline solution and detached dirt from the surface of the steel strip.
5.How clean is the surface of the steel strip after electrolytic cleaning?
The surface of the strip steel after electrolytic cleaning is extremely clean (the reflectivity can usually reach more than 90%), which can ensure that no carbon black is generated in the subsequent annealing furnace due to the volatilization of residual oil, or that the zinc coating has good adhesion to the substrate.