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M11 - Electrophoretic Coating System and Coating Processes


Project No.: M11

Project Title: Electrophoretic Coating System and Coating Processes


1. INTRODUCTION

Electrophretic process enables a uniform clear or colour coating to be applied over complex shaped metals in order to protect, endure and enhance.

Electrophretic lacquer is diluted in water to form an emulsion that is stable in a specific pH range. The electrophoretic bath contains immersed anodes and the workpieces to be coated are immersed in the solution and are connected to the cathode by the application of a DC voltage. During the coating process, a very thin layer of alkaline solution is created around the cathode, this causes coagulation of resinous solids within the alkaline layer. This forms the coating around the workpiece. This coating is electrical insulator and when a certain thickness is reached, the insulation reduces the current to the extent that electrolysis ceases and so terminates the deposition process. A colour coating is obtained by addition of a dyestuff to the bath.

2. TECHNICAL OUTLINE

The following sequence is to be carried out in an electrophoretic coating operation. The workpiece to be coated must be free from dirt, grease and oxide layer.

Electrolytic degreasing
DI water rinsing
Electrophoretic coating
Double DI water rinsing
Rinsing with rinsing aid solution
Curing in a forced air circulating oven

3. SPECIFICATIONS

  • Make up of the electrophoretic solution
  • DC power supply
  • Filtration and ultra-fine filtration
  • Rinsing aid solution
  • Curing
  • Electroplating on metals and plastics

4. REQUIREMENTS

Student are required to set up a small-scale electrophoretic system based on the given outline and specifications. A complete coating line is in W401 for your reference.

After setting up the system, you are required to produce different colors of coatings on metallic and plastics surfaces. In order to give a lustrous appearance, all workpieces are to be plated with bright nickel. The plastics articles have to be made conductive prior to electroplating.