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Principle of chemical degreasing of hot dip galvanized

- Jul 31, 2018 -

Principle of chemical degreasing of hot dip galvanized

(1) saponification

(CHsC0) CHs +3 NaOH-3 C,HsCOONa + CHs (OH) 3

Saponification is the chemical reaction of soap and glycerol are soluble in water, they dissolve into the aqueous solution of alkali and off the surface.

(2) emulsion

As the emulsifier in the alkali solution (prior to join emulsifier and saponification reaction generated soap), the effect of the plate is not all the saponification of animal and plant oil oil film, mineral oil or synthetic membrane lipid of the saponification and not all the saponification of saponification of oil film, into a lot of small oil beads, from the plate into the lye, which is emulsified.Emulsifying process is a physical change process.

Principle of hot dip galvanizing electrolytic degreasing

When the steel belt passes through a channel containing an alkali solution, the steel belt is used as an anode or cathode in the case of direct current.

When the steel strip ACTS as a cathode, the surface is reduced and hydrogen is precipitated: 4H0+4e=2H t +40H

When the steel strip ACTS as an anode, the surface is oxidized and oxygen is precipitated: 40h-4e =0, t +2H0

Hydrogen and oxygen bubbles tear the oil film apart, making it a small oil bead, and the bubbles grow larger and take the small oil bead off the surface.The emulsifying process is a combination of chemical reaction and physical change. The above two chemical equations are expressed as follows: reaction: formation of small oil beads; separation of hydrogen or oxygen bubbles from the plate into alkali solution; visible hydrogen and oxygen bubbles; electrolysis and degreasing process; water electrolysis; this is the physical change.

The emulsifying ability of electrolytic degreasing is stronger than that of chemical degreasing due to the action of large number of bubbles.

The steel strip is electrolytically degreased, usually by means of intermediate conductor combined with electrochemical degreasing.The so-called intermediate conductor method refers to the steel strip as the intermediate conductor between the cathode plate and the anode plate.The so-called combined electrochemical oil removal refers to: when the steel belt passes through the channel between the cathode plates, the steel belt ACTS as the anode; when the steel belt passes through the channel between the anode plates, the steel belt ACTS as the cathode; when the steel belt crosses, it ACTS as the anode and cathode.In this way, the steel strip is used as an anode and two electrochemical deoiling methods as a cathode.

The polarity of different plates shall be changed regularly, so that the original plate as an anode becomes a cathode, the original plate as a cathode becomes an anode, and the polarity of the plate will be reversed after the next switch.