Electroplating, electrocoating, electrodipping

A. Hi Mimi. Electroplating means applying a metallic coating such as gold, nickel, or zinc. Electrocoating means applying an organic topping (paint) by the process of electrophoresis, such as is done in the priming of automobiles. Electrodipping has no established meaning as far as I know.

I would expect electroplated metals to have more hardness and wear resistance than electrocoated organic finishes.

A. Hi Sherwin. I would suggest that you avoid the acronym 'EDM' since is is widely used to mean "Electrolytic Discharge Machining", and I've never seen it used to mean 'electrodeposition method'

Yes, electroplating refers to the deposition of metals whereas electrophoresis is used to deposit organic materials like paint.

A. Hi, Alison. I had to look it up, and I found that "Phoretic" actually just means "transport", so "electrophoretic" only means that electrical charges are causing something to be transported.

When I've have heard people use the term 'electrophoretic' for the last 30 years, they always meant electropainting/electrocoating; but apparently the term is not limited to organic coatings as I had incorrectly thought. The Allison Electrophroretic Process deposits nickel aluminide coatings, without the metal dissolving into positively charged ions as in electroplating -- but I am not actually familiar with the process at all. Sorry!

Regards,

Thank you for the information and trying to help. I understand this process on a surface level, but struggle to understand it on a very intimate or technical level. Unfortunately, when we ran into problems there was little (read no) reference material I could find to pull from and investigate. Thank you very much for the efforts.

A. Hi again. John Tuohy references the process in letter 13420, "Making Stable Graphite Suspension for Coating", so he knows something about it, and we could probably draw him back to this conversation.

It seems to be covered by US patent 5976337 by Allison Engine Co., and to be used by Rolls Royce for proprietary powders.

There is a very detailed 98-page investigative report available for free at
oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA061270
(If the link breaks, let me know -- I've learned to keep a copy!)

Regards,

A. Hi Andy. I've learned to be cautious about calling things impossible, but I think you'll find it impractical. To my knowledge, in addition to the special paint, you will need high voltage rectifiers (dangerous for manual, home, operation), a capable ultrafiltration system for resin recovery, suitable diaphragms, DI or RO water systems, possibly post-dyes, ovens, and sealing wax, and other fancy stuff. Oh!

adv.
I've never personally heard of anyone doing it at home scale :-)

Regards,

A. Hi Jim. Although people coin slang for their own convenience, and we can't stop them from using it to mean what they choose it to mean, most of us do not regard "electrocoating" to mean "powder coating".

To most of us, electrocoating (or e-coating, electropainting, electrophoretic lacquering, CED [cathodic electrodeposition]) is a very different process from powder coating.

In electrocoating an electrified article is placed into a vat of water-based liquid which has chemicals in it which the electricity at the surface of the parts converts into an insulating paint which coats the surface. One of the most common uses for electrocoating is priming automobile frames, because the water gets everywhere, the electricity gets everywhere, and a protective paint layer is deposited even in hard to reach spots.

In powder coating, the part is just electrostatically charged so it will attract the powder that is sprayed in its direction. The powder sticks by this electrostatic attraction. Then, when the parts are put into an oven, the powder melts and flows to cover the part with a skin of paint.

Regards,

A. Hi Mohameed. Generally a lot of people use the word 'plating' as a short version of 'electroplating' (depositing metal on the surface) and coating as a short version of 'powder coating' or 'electrophoretic coating' (depositing organic coating materials on the surface.

But these are not specifications, they are more along the lines of slang & shorthand, and I would not read too much into them. If someone wrote that they put a 13 micron coating of cadmium onto a part, I don't think anyone would correct them; but if someone said they put a 2 mil plating of epoxy-polyester powder on the part people might correct them :-)

Regards,