CED

Cathodic Electro Deposited coating is used extensively in the automotive industry. In this process, the component after phosphate pre treatment is dipped in the bath of Ecoat chemicals and given an electric charge.

The coating gets deposited on the component. The component is removed from the bath, washed and then baked.

A complete Ecoat system consists of the following: Pre treatment line Ecoatline Material handling system Oven It also requires the following auxiliary equipment: Hot water generator RO water system DI water system Laboratory Effluent treatment plant Pretreatment: Pre treatment line will consist of the following stages: Knock off degreasing Degreasing Water rinse Water rinse Activation Phosphating Water rinse Recirculated DI water rinse DI water rinse It will also have circulation, heating, filtration etc, wherever required.

The Ecoat line will consist of the following stages: Ecoat Permeate rinse 1 Permeate rinse 2 DI water rinse It will also have prefiltration, ultrafiltration, chiller, rectifier and anolyte system.

MaterialHandling For the SME segment the programmable hoist type system is the most economical. This is also popularly called the transporter system or the transporter wagon. The products duly loaded on the jig are carried from one tank to the other in a pre­programmed sequence and pre­defined time. For mass produced similar products, conveyor system is more suitable.

Baking oven The oven can be electric, diesel or gas fired. The diesel or gas fired ovens are with stainless steel heat exchanger or directfired.Forcedconvectionisaustfortheoven.

The auxiliary equipment is available from a large number of sources.

To be able to design a system, the following information is required: SizeofthecomponentSurfaceareaofthecomponentWeightofthecomponentNumber of components to be coated per hour Numberofworkinghoursperday In some cases, simply the tank size, the expected surface area per batch, weight per batch and the number of batches per hour is also enough.

The Cathodic Epoxy Electrocoating process is outlined in brief detail here.

A DC charge is applied to a metal component immersed in a bath comprisoing of oppositely charged paint particles.

The paint particles deposit on the component to a point where the coating reaches the desired thickness and an even, continuous film is formed over every surface, crevice and corner.

On attaining desired thickness, the film insulates, resulting in stopping of attraction between paint particle and the component, thus completing the process.

Depending upon the end use, you can choose either protective, decorative or a combination electrocoating

Types of Electrocoat Anodic and Cathodic ANODIC: For Excellent Colour and Gloss control, combined with economy The component to be coated works as an anode with a positive electrical charge attracting negatively charged paint particles in the paint bath.

Small amounts of metal ions migrate into the paint film, thus limiting the performance properties.

Anodic Coating finds it’s main use in products meant for interiors or moderately aggressive exterior environments.

CATHODIC: High Performance Coatings with excellent corrosion resistance The part to be coated is given a negative charge, which attracts positively charged paint particles.

The reversing of anodic polarities greatly reduces the amount of ions entering the cured paint film and this enhances the performance properties of cathodic electrocoated products.

Cathodic electrocoating are high performance coatings and can withstand the harshness of exterior environment.

Anodic and cathodic coatings can be done by using both epoxies and acrylics.

ELECTROCOATING VS POWDER COATING AND LIQUID SPRAYS ENVIRONMENTAL ADVANTAGE Eco­friendly Free of heavy metal with little or no Hazardous Air Pollutants (HAPS) and very low levels of organic solvents.

Being water based coatings, they have very low Volatile Organic Compounds (VOC),ranging from 0.012 kg per litre up to 0.360 kg per litre with most products below 0.120 kg per litre.

Practically no solid waste No fire hazard.

Electrocoat is a clean system not requiring any disposable suits, respirators, and other safety equipment to protect workers from airborne hazards.

TECHNO­ECONOMIC ADVANTAGE Cathodic epoxy electrocoating is highly corrosion resistant. A 20­micron dry film thickness can withstand as much as 1000 hours salt spray test.

Uniform Coating: Electro coating has the ability to give very even coating with variances ranging to only 1­2 microns.

Coating of Complex Parts: Electro coat system has the versatility to coat highly recessed and complex surfaces, which are not amenable to powder coating or liquid spray system.

Higher Transfer Efficiency: The process being a closed loop process allows transfer efficiency of more than 95%, with much reduced waste water streams.

Very Low Incidence of Rejects: Being electronically controlled, human errors play a very little role thus minimizing rejection rates which could be as low as zero.

No special skills required for handling the plant and production.

Higher Productivity: No other paint system can match the through­put capacity of an electro coat system.

Quality Edge: As Electro coat films are controlled by voltage adjustments the deposition stops, once the metal is insulated. No other organic coating system can be controlled with the film uniformity as in Electro coating system.

Ease in Handling: Even the uncured paint is dry enough to allow human touch and careful handling.

LIMITATIONS Electro coating can be done only on metals.

Only one color is economically viable in one set­up/line.

Initial capital cost is higher in comparison to powder coating and liquid spray systems.

Special care required to prevent air entrapment during paint deposition process in paint bath.

More energy intensive process than powder coating and liquid spray, as the circulation pump to agitate the paint bath has to run 24 hours, irrespective whether there is production or not.

Surface defects of component to be electro coated cannot be covered.

OPERATIONAL DISPLINE

1) Never enter CED tunnel while rectifier is ON 2) Do not add paint / additives directly to bath paint. It must be added through dosing pump with delivery at pump suction.3) Do not use any contaminated bucket for paint dosing. A separate bucket (100 liters) to be arranged separately for CED dosing.4) Do not dip any wooden / mild steel stirrer either in bath or supply paint. Use either plastic or SS stirrer.5) Do not run production with anolyte circulation OFF.6) Do not turn off UF feed pump without proper flushing of UF modules7) Do not keep the UF modules on paint without circulation for more than 15 min (or KOCH recommended time)8) Do not run turbid UF through pump mechanical seals.9) Do not run production with CED tank exit spray OFF.10) Do not load components with rust.11) Do not load components with heavy oil without proper wiping.12) Do not allow any foaming in CED tank.13) Do not add pigment paste without stirring the paint in barrel.

Homogenize paint in barrel. Take out required quantity in bucket. Add some water to dilute it before dosing. Do not add water in supply barrel. It will result into hard settling of paint.14) Do not add solvent additive / pH stabilizer immediately after paste or emulsion through dosing line without flushing with DM.15) Do not start the production till DM4 and DM3 stages in PTC are fully operational.16) Do not allow bath temperature to exceed 35 deg.C as it may create harm to UF modules.17) Do not run production if bath temperature is less than 25 deg,C18) Do not run the production if oven temperature is not achieved as per set point as under cure gives poor film properties.19) Do not allow fallen parts to remain in rinses for long time.

Do’s 1) Test all required parameters of CED bath and rinses every day before start of production 2) Preferably complete entire addition well before start of production 3) CED sample to be taken from sampling point. Rinses sample to be taken from top of the tank if sampling is point not provided.

4) In case of addition sequence, add emulsion followed by paste. It is good practice to flush pump with DM water after addition of individual components Flush pump thoroughly after addition is complete. (i.e Dose DM water through dosing line).