Thread: Blackening metal vs powder coating

Curious what is a more durable finish - powder coating vs blackening by heating and rubbing on oil like in this video:
https://www.youtube.com/watch?v=hz6wdvraC-g

That blackening process is like seasoning a cast iron or carbon steel pan and they are very durable - I use metal utensils in those pans with no issues.

It all depends on what the environment the item concerned is to live in.
Powder coating, while being a decorative finish, is only as good as the applier allows it to be. Any pinholes, will allow the metal to corrode/rust and the coating to peel away. Have a look at some of the seaside homes that have powder coated balconies, boat trailers etc.
If the item is to be inside, then powder coating will be fine, an oil blackened item would probably rust also if it was placed in a rusty location and not cared for.
Kryn

Also depends on the interpretation of durable.
Blackened stuff only has a thin layer so won’t chip - so is effectively a harder layer than powder coat. Good powder coat will last for years outside in the sun and rain without degrading much more than a bit of surface oxidation.
Blackening wouldn’t last a month without needing the oil reapplied.
Add a salty environment and it wouldn’t last a week.

Steve

Powder is more durable but actual use depends on a bunch of factors like
- the ambient environment - powder coating is better in moist or corrosive environments
- amount of handling - powder coating wins on that score
- do you want to be able to protect close fitting parts such as threads - certain types of blackening will be much better than powder coating
- the actual blackening process used.

If you are talking a "paint on" blackening agent or a hot dip into oil then it's not going to last that long compared to powder coating.
If its a hot caustic or cold fume blueing blackening process it will last longer but still not as long as powder coating. I have fume blued blackening parts that have been in my shed for 9 years and are still OK others have developed faint rust on them. If the part is small its dead easy to convert the rust back to black oxide - just chuck it into boiling distilled water and then polish it up lightly again and add some oil.

The tool post and rotary table bracket were made and cold fume blacked back in 2012
RTbracket.jpg

Thanks all for your replies. The item would be indoors and not in a 'salty' area.

Im inquiring with a few places regarding powder coating - what is the sandblasting step for? Is that worth doing?

Usually, who removes the mill scale/blue primer when sending things off to be powder coated?

Originally Posted by qwertyu

Thanks all for your replies. The item would be indoors and not in a 'salty' area.

Im inquiring with a few places regarding powder coating - what is the sandblasting step for? Is that worth doing?

yes its definitely worth doing and it's to get a really clean surface to improve powder coating adherence.

Usually, who removes the mill scale/blue primer when sending things off to be powder coated?

Its better to get them to do it because if it goes pear shaped then you have comeback - if you do it they can say it was your problem.

Originally Posted by qwertyu

Thanks all for your replies. The item would be indoors and not in a 'salty' area.

Im inquiring with a few places regarding powder coating - what is the sandblasting step for? Is that worth doing?

yes its definitely worth doing and it's to get a really clean surface to improve powder coating adherence.

Usually, who removes the mill scale/blue primer when sending things off to be powder coated?

Its better to get them to do it because if it goes pear shaped then you have comeback - if you do it they can say it was your problem.

What is the application BTW?

You have specified two extremes of protective coatings that I wouldn't normally expect to see compared.

Powder coating provides a thick, durable finish. I'd generally associate it with things that need to cop a bit of a beating. Not a perfect surface finish but matches well with the above usage. No good where precise mating surfaces are required. Reasonably expensive for one off pieces.

I haven't used oil blackening personally but we're talking about a light duty DIY coating. Probably something I'd expect to see more on artistic items or where some protection is required at minimum cost with the expectation of ongoing maintenance.

In between these two extremes there are all manner of coatings that might be better suited to the application than either of the above.