electrophoretic painting

Teknik Kimia Universitas Brawijaya

ELECTROPHORETIC PAINTING

www.themegallery.com

Teknik Elektrokimia

Dosen : Vivi Nurhadianty

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E-COATINGIt is a process where a metal part is

immersed in a water-based solution containing a paint emulsion. An electric voltage is applied to the part causing the paint emulsion to condense onto the part. A part can be painted both inside and out, wherever the liquid is able to reach a metal surface. The coating thickness is limited by the applied voltage.

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SIMPLE PROCESS 1. it begins with particles which are well

dispersed and able to move independently in solvent suspension

2. the particles have a surface charge due to electrochemical equilibrium with the solvent

3. there is electrophoretic motion of the particles in the bulk of the suspension

4. a rigid (finite shear strength) deposition of the particles is formed on the deposition electrode.

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Medium Water based contain 10 % solidThe paint is a polimer containing : 1. Acidic or basic group 2. Some inorganic solid as copper

chromate, titanium dioxide3. Organic pigmen

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Mechanism

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Mechanism

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reaksi pada catoda atau anoda

Tergantung dari muatan micele/ resin polimer

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EXPERIMENTAL

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Anoda

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General Arrangement

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THE SURFACE COATING OF CAR BODIES

Step 1 - PrecleaningThe car body is assembled from imported

metal panels and cleaned with kerosene to remove dirt and grease.

Step 2 - PhosphatingThe metal is treated with phosphoric acid

This gives a mixture of zinc phosphates. The electrocoat paint binds better to these zinc phosphates than to the steel alone, and the zinc phosphates corrode much slower than the pure steel.

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THE SURFACE COATING OF CAR BODIES

Step 3 - ElectrocoatingA mixture of resin and binder and a paste

containing the pigments are fed into a tank. The vehicle is then lowered into the tank from an overhead conveyor and an electric current applied. This car body becomes the cathode and the tank the anode in an electrocoating reaction that results in a resin polymer being very tightly and evenly bound to the metal surface of the car body

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Step 4 - RinsingThe vehicle is rinsed several times,

both with water and with a weak paint solution, to remove a thin coat of paint that clings to the surface but hasn't bonded to the metal. If this wasn't removed then the car would have an uneven, messy coat of paint.

THE SURFACE COATING OF CAR BODIES

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Step 5 - BakingThe car body is then baked to 170 -

180oC in an oven. This causes the different polymer chains to crosslink (i.e. bind to each other in many places) forming a very strong, flexible, interconnected network of polymer over the whole surface of the car.

THE SURFACE COATING OF CAR BODIES

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Keuntungan The paints are water based, non

toxic, no fire risk, effulent disposal problem minimal

Easy to obtain complete coverage of even the most complex surface

Well suited for automation

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Perbedaan

electroplating

•Mediumnya mengandung ion logam (inorganic)•reduction of metal ions in solution to solid metal•Melapisi dengan logam •Waktu lebih lama (hingga 1 jam)

electrophoretic

•Mediumnya mengandung padatan polimer (organic) •polymer precursor is deposited by electrochemical polymerization•Melapisi dengan cat •Waktu sngat singkat (2-5 menit)

Teknik Kimia Universitas Brawijaya