Pretreatment is the foundation of any high-quality coating line. Here is a technical breakdown of how degreasing and rinsing work to ensure perfect surface adhesion.

1. Degreasing Principles

The goal is to remove oils and contaminants to create a pristine surface. We utilize four primary methods:

• Chemical Degreasing: Uses alkaline agents (Sodium hydroxide, sodium carbonate, sodium phosphate) to trigger a saponification reaction, turning insoluble fats into water-soluble soap and glycerol.

  Formula: (C_17H_35COO)_3C_3H_5 + 3NaOH longrightarrow 3C_17H_35COONa + C_3H_5(OH)_3

• Electrochemical Degreasing: The workpiece acts as an electrode. Electrolysis generates (cathode) or (anode) bubbles that mechanically scrub and lift oil off the surface.

• Cathode: 2H_2O + 2e^longrightarrow H_2↑ + 2OH^-

• Anode: 4OH^4e^longrightarrow O_2↑ + 2H_2O

• Emulsion Degreasing: Uses organic solvents and emulsifiers. Solvents dissolve the grease, while emulsifiers prevent the oil from re-depositing onto the workpiece.

• Ultrasonic Degreasing: High-frequency vibrations create "cavitation bubbles." When these bubbles collapse, they generate micro-jets that blast stubborn contaminants away.

2. Water Rinsing Principles

Post-degreasing rinsing is critical to prevent cross-contamination:

• Dissolution & Dilution: By using circulating or immersion rinsing, residual chemicals and decomposed oils are dissolved and carried away, reducing impurity concentration to near zero.

• Mechanical Scrubbing: The physical force of water flow—especially in high-pressure spray systems—dislodges micro-particles and stubborn residues.

Keywords

• Surface Treatment, Pretreatment Line, Saponification, Cavitation Effect, Alkaline Degreasing, Electrostatic Powder Coating, Water Curtain Spray Booth

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#SurfaceTreatment #PowderCoating #IndustrialFinishing #DegreasingProcess #CoatingLine #ManufacturingSolutions #ShengTaiPainting #Pretreatment #CorrosionProtection