E-coating vs. Powder Coating vs. E-coating Plus Powder Coating

A. Jagdip,
You didn't mention what spec you are trying to achieve. You also did not mention anything about pretreatment.
The CED and powder will only be as good as the conversion coating that is beneath them.
In my opinion, the best combination is a zinc phosphate pretreatment with a cationic epoxy e-coat primer AND powder.
The chassis can be e-coated with or without rivets and bolts. You'll need to consider masking and will also need to consider drainage as the chassis gets more complex.
Your paint supplier should be able to address film build and cost.

A. Venkat: The end use of your product will determine whether e-coat should be used as a top-coat. Cationic epoxies offer excellent salt spray performance but have poor UV durability. Acrylics have good UV durability but do not perform as well in salt spray.

? Hi Arijit. Please tell us what the parts are that you wish to coat (application, size & shape), and what the production situation is (x parts per hour, y hours per day, etc.)

Regards,

Q. Parts are 2 foot hollow tubes of 1 inch dia., production 200 per 8 hrs; shapes are a little bit bent (Turning Tubes of trucks. Please suggest which will be the best cost effective coating having same Zn phosphate pretreatment--CED coating black or Powder coating black.

A. Hi again. 200 parts in 8 hours is 25 per hour or one every 2.4 minutes. This is a modest production rate and manual powder coating would probably be fine. It's also a low production rate for e-coating -- if the rack held, say, 4 or 5 parts, you'd only need to process 5 or 6 racks per hour. But you could integrate the e-coating with the phosphatizing, and probably would not be as easily able to integrate the powder coating with the phosphatizing.

My own feeling is that e-coating would be slightly less labor intensive, slightly less expensive in materials, and slightly more reliable (free from defects). The e-coating equipment would probably cost significantly more, so you would need the production run to last long enough to offset the capital cost difference.

Second opinions welcome, especially from anyone who has done both :-)

Regards,

A. Hi Gunjan. As one tiny part of your research I'll offer my opinion that powder coating will probably prove adequate. But what process do your competitors use and what do you think of their appearance, corrosion resistance, and durability? There is a stewardship issue here: I know a bit about e-coat vs. powder coating, but few if any of we readers is likely to have the experience and understanding of the kettlebell industry which should be brought into evaluating the alternatives. Good luck.

Regards,

A. Hi again. I already answered your question -- powder coating should probably be okay -- but you didn't answer mine :-)

What finish do your competitors apply, and what do you think of it based on actual field experience? Scuffing, chipping, UV sensitivity? Exactly what appearance are you seeking? Once again, I'm pleased to give you a free off-the-cuff guess based on general industry experience, but what are you going to do with that guess? I don't know if you only permit indoor use, or they might be left out in the grass; I don't know if users bang them together and chip them; I don't know what grade of steel or iron they are made from. You can ask for guesses & hints for further evaluation, but that's about it :-)

Regards,

A. Hi Jamie, thanks. Apple and companies like it which manufacture in China have full teams over there. You are unfortunately experiencing what people call "throwing it over the wall" -- you're going to get something, but you're not sure what, maybe cast steel or ductile iron or cast iron. Now you want to finish it, but don't know if it may have silicon embedded in it, nor what the mechanical finish will be.

You can specify zinc phosphating followed by polyester or epoxy e-coating, with a post-dye to give it a somewhat metallic red look. But it has to be something your casting contractor can accept responsibility for, as split responsibility is difficult to manage with domestic shops but will be impossible with you here and your contractors in China.

Alternately, you can retain a testing lab to try to reverse engineer the finish on your competitors' products, but we can't publicly comment on or speculate about what your competitors are doing beyond what it says in their sales literature because, as we've said on some other threads, we don't know the responders so we can't let posts here wander into potential crowd sourcing of industrial espionage :-)

Regards,

Hi again. No paint adheres infinitely well -- it's always possible to scrape it off or chip it off in some fashion. But you are looking for fitness-to-purpose, not infinite adhesion, and e-coating on a surface which has been properly mechanically finished and properly phosphated should be fine.

3-step iron phosphating is probably good enough, but 7-step zinc phosphating is always better.

If silicon is imbedded in the castings, adhesion would likely be poor. Mechanical treatment like vibratory finishing will probably remove it; but an acid dip which includes fluorides might be required; I really can't say, and don't know whether others can without testing or not. Good luck.

Regards,

A. I may have some answers, paint in general even E-coat will not adhere well to bare steel. To promote adhesion a treatment such as iron or zinc phosphate should be applied. A zinc phosphate coating forms through a precipitation reaction as the phosphoric acid at the boundary of the substrate is consumed resulting an increase in pH. Cleaner residue due to inadequate rinsing will also precipitate a zinc phosphate layer which will have poor adhesion which no subsequent coating will overcome. E-coat usually epoxy based will stick very well to the zinc phosphate. Actually epoxies will stick well to many substrates hence their use as adhesives.
As it appears you want a bright color, candy apple red, a finish coat would most likely be needed. Polyester would be a good choice or if you want a higher end coating with even better adhesion you could use a urethane. From what little I know of powder coatings, they tend to be applied thicker than a conventional liquid coating, adhesion may be adversely affected by this choice.
Good substrate choice, subsequent processing such as cleaning, treatment choice, and finally type of coating and application method could all affect adhesion.
I currently am employed on a coil coating process, the end product is stamped, bent, and/or rolled formed, and thus proving that a properly applied organic coating can have very good adhesion under some pretty brutal conditions.

A. Hello Sy. If you have trellises that have been e-coated and subsequently powder coated (and assuming that it was done well and with proper pretreatment, and the top coat is not epoxy with it's poor UV resistance), that's probably a pretty robust finish. 11-12 mils sounds like a thermoplastic (teflon, nylon, vinyl) coating rather than thermoset. If you don't scratch them during installation, they should be fine. Are they aluminum, steel, or what?

We do warn though, that you can post your clearly understood questions here and often get good answers ... but if you post a question that you don't really understand, hoping the answer will help you understand the question, it may not work that way :-)

I'm not quite sure which is the case. Good luck.

Regards,

A. Hi Praveena. I already offered my opinion above that e-coating involves more capital cost than powder coating; others are welcome to respond if they wish. But as already mentioned on this page and on the inquiry submittal form, our readers tell us they hate abstract questions, so I don't know if they will.

Your own actual situation is no doubt interesting -- please tell us about it :-)

Regards,