Go and look at the vent you are replacing. If there are small grey chips at the corners, you are looking at bare steel through a sprayed-on finish.
What each one is
Powder-coat starts as a dry powder. It is given an electrostatic charge and sprayed at the earthed steel, so it clings evenly, including round edges and into corners. Then the whole part goes into an oven. The heat melts the powder into one continuous skin that is chemically bonded to the metal.
Enamel is wet paint. Sprayed on, left to cure, done. It sits on top of the steel the way paint sits on a wall.
Why that shows up at the corners
Wet paint is pulled by surface tension while it cures. It thins out over sharp edges and pools slightly in flat areas, so the corners end up with the least coverage and take the most abuse.
Powder behaves the opposite way. The electrostatic charge actually draws it toward edges, so coverage there is as good as anywhere else. Then the bake bonds it. There is no thin corner to start the chip.
That is why a powder-coated part tends to wear down instead of flaking off, and why a ten year old enamel vent looks shabby in a specific, recognisable way.
Where it matters most
- Floor registers. Walked on, vacuumed over, furniture dragged across. The single worst case for a finish that sits on the surface.
- Access panels. Opened and closed, latch turned with a screwdriver, door handled. Our steel panels use a 4-stage powder-coat for that reason.
- Damp rooms. Every chip is a place for rust to start. A continuous bonded skin has fewer of them.
Batch-to-batch colour
A quieter advantage. Powder is mixed as a dry formulation and baked at a controlled temperature, so one run matches the next closely.
This matters more than it sounds if you are doing a house a room at a time. Three white vents from three separate orders should read as one white, not as three slightly different ones. Which is also why we only run one finish per category: brown on floor registers, white on everything else.
Painting over it
Powder-coat is smooth, which is the point, and it is also why paint needs help to grip. Scuff it, prime it with a bonding primer, then paint.
Skip the scuff and the primer and the paint will look fine for a month and then peel in sheets. Full method in how to paint a vent cover.