Powder coat vs wet paint: which finish to call out on a fabricated part

How each finish is applied

Powder coat is a dry polymer powder sprayed with an electrostatic charge onto a grounded part, then cured in an oven, usually around 350 to 400 F for ten to twenty minutes. The powder flows into a continuous film as it cures. There is no solvent, so there is nothing to flash off and the film can be built to a few mils in one pass.

Wet paint is a liquid coating, solvent or water based, sprayed in one or more coats and air dried or baked at a lower temperature. Primer plus topcoat is common. Because each coat is thin, a durable wet paint system takes more passes and more handling time than a single powder coat.

Where powder coat wins

• Durability on steel and aluminum that will be handled, bolted, or outdoors: the cured film resists chips and chemicals better than most single-stage paints.
• Uniform coverage on welded frames and tube: the electrostatic wrap pulls powder onto edges and into corners that a spray gun reaches unevenly.
• Thickness in one pass: 2 to 4 mils is routine, which hides minor grind marks and mill scale texture on a weldment.
• No solvent emissions, which is why most sheet metal and fabrication shops run a powder line in house and quote it with the parts.

Where wet paint wins

• Parts that cannot take the oven: assemblies with rubber, plastic, electronics or a press-fit bearing already installed, and thin or long parts that would warp at cure temperature.
• Exact color matching to a corporate or automotive color: a wet paint can be mixed to a PMS or RAL reference; powder comes in catalog colors and a custom match is a minimum-order item.
• Field repair: a wet-painted part can be touched up with the same paint; a chipped powder coat is usually touched up with a matching wet paint, which never quite matches the texture.
• Very large weldments that exceed the oven at the shops available to you. Ask on the request how big the finishing oven is before you specify powder on a 20-foot frame.

What to put on the drawing

A finish callout the shop can quote names the process, the color, the gloss or texture, and the film thickness if it matters. For powder coat that is a color reference (a RAL or a catalog name and number), the texture (smooth, fine texture, wrinkle), and a thickness range if the part has a fit that the coating affects. For wet paint it is the paint system or a spec, the color reference, and the gloss level.

Say what must stay bare. Threaded holes, ground pads, electrical bonding faces, and any surface that mates to a machined part are masked only if the drawing calls them out. An unmarked tapped hole gets coated, and chasing threads after the fact is a charge and a delay.

If the part is sheet metal with PEM hardware, say whether the hardware goes in before or after finishing. Most shops install hardware after powder coat so the threads stay clean, and they will mask the hardware holes accordingly.

Powder coat vs wet paint at a glance