E coating vs Zinc plating, long term which is the better option?

A. Hi, Gregg. If one were "better" than the other, the latter wouldn't exist. Selection of one process over another must take into account the kind of parts and the exposure situation. For example, if the parts get scratched, zinc plating will still provide sacrificial protection, while electrocoating does not. But a non-sacrificial coating like E-coating will probably easily outlast a thin sacrificial coating like zinc plating if you try to judge it by salt spray test rather than real-world exposure. What are the parts and the situation? Thanks.

Regards,

A. Hi Michael. E-coating will probably outperform zinc plating in salt spray testing, which is one measure of rust resistance. That does not change the previous answer though, that zinc plating is a sacrificial coating whereas e-coating is only a barrier layer coating, and it isn't possible to make proper suggestions in the abstract.

Luck & Regards,

A. Zinc plating is one of the least expensive and most versatile corrosion resistant finishes, especially for small hardware, because the items can be plated in bulk and with relatively simple equipment, yet can be readily automated. Zinc-nickel is an alloy finish that is somewhat more expensive, and somewhat less commonly available, but not drastically so. Still, it does no good to get estimated costs if the service isn't actually available, so the best way to proceed is usually to get quotes. Good luck.

Readers: In posting questions please try to heed the repeated requests of our regular responders that you not post abstract questions, but carefully detail your own situation.

Regards,

A. Hi Viktoriya. I have expressed my opinion that zinc plating and chromating is probably less expensive than e-coating and that the chief reason is probably that many of your parts can be plated in bulk rather than having to be individually jigged for e-coating. Beyond that, abstract ideas about cost don't go very far -- you would need to cost out an e-coating line and the labor and chemicals it requires to operate.

Zinc plating is a sacrificial coating which offers corrosion resistance advantages in rough service, and the abrasion resistance of metal. But phosphatizing followed by e-coating will probably offer greater corrosion resistance in most applications. You know what the plating looks like because you already do it. The e-coating will look like paint, but it can look like pretty nice looking paint :-)

Regards,

Dear Mr. Mooney, I appreciate your advice!

A. The two work differently. E-coat is a barrier, while zinc is a sacrificial anode. Zinc will tend to degrade over an area, whereas e-coat tends to pit, rather than a large patch. Been a while since I've worked with e-coat, but if I recall testing, e-coat lasts a little longer. Just recognize that the parts down the road will look very different, and pits may be a more serious failure mode.

A. Hi Ryan. Electroplating, galvanizing, and other finishes of solid metal, and conversion finishes like phosphating, chromating, and anodizing, must react with the base metal and can only be done onto bare metal. Because of the very high process temperatures involved in ceramics, they usually can only be done on bare steel. An actual ceramic coating is like covering the component in melted glass, but some paints call themselves 'ceramic' with no justification except having some ceramic particle grit in them.

In general, organic finishes like e-coating, paint, and powder coating can be done on top of metallic finishes -- but that does not guarantee compatibility of the particular metallic finish and the particular organic and its deposition method. Please name an actual part with an actual finish and why you consider it less than satisfactory, and please introduce yourself as a hobbyist wanting to restore old parts or a plant manager wanting to build a production line or whatever, and people may be able to give specific advice. Good luck!

Regards,

A. Hi Rao. Sorry I don't know the coefficient of friction for these two finishes, but yes they could be quite different. The new finish is a thin layer of paint and the old is metal. Regardless of the coefficients though, I wouldn't expect paint to resist wear/friction for very long without either wearing off or gumming up.

Regards,