The authoritative public forum
  for Metal Finishing since 1989
  

  -----

E Coat Definition

Can someone tell me what "E" coat is? Thank you

BOB L [surname deleted for privacy by Editor]
- ELKHART, Indiana
1999

---

"E-coat" is electrocoating, also known as electrophoretic painting or electropainting. It's an organic finish which is often applied as a prime coat on steel. The part is immersed in an electrified tank, and the reaction between the electricity and the solution causes the paint to deposit.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

I have a requirement for a 20 year finish on cold-rolled steel, NOT using tin or zinc, and nickel is too expensive. Is "E coat" appropriate in my application?

Kevin K [surname deleted for privacy by Editor]
- Mesa, Arizona
1999

---

You haven't told us why tin and zinc are not appropriate, Kevin. And not knowing the criteria that makes them inappropriate, it's hard to say whether e-coat is appropriate. 20 years of benign indoor exposure doesn't sound too tough, but 20 years of outdoor exposure could be quite a problem.

As a general rule, the advantage of plating over organic finishes is that the adhesion is infinitely better because the bond is metallurgical, rather than a simple mechanical key, and the coatings are much thinner, making them more appropriate for tight fitting things like hardware threads. Further, the sacrificial coatings like zinc continue to protect the substrate even if a scratch penetrates all the way through whereas as an organic coating offers strictly barrier-layer protection.

This is not to say that organic coatings do not likewise have advantages over plated coatings, but just to highlight what you are giving up so that you can see whether your criteria, which we're not yet privy to here, are still met.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
1999