To powder-coat metal, clean, degas, ground, spray electrostatic powder, then bake to the powder’s cure schedule.
Powder coating metal gives a hard finish, sharp color, and solid corrosion resistance with minimal mess. This guide walks through tools, prep, spray technique, and curing. You’ll also see common defects and fixes. Every step is field-tested and tuned for small shops and hobby spaces.
Powder Coating Metal Basics
At its core, a dry thermoset powder is charged and sprayed onto a grounded part. Heat flows and cures the film into a single, tough layer. You control three things: surface prep, electrostatic transfer, and time-at-temperature. Nail those, and parts look pro-grade.
Before we spray, set up your gear and space. The table below is a checklist to get you rolling without backtracking.
| Item | Purpose | Notes |
|---|---|---|
| Powder gun (corona or tribo) | Charges and delivers powder | Start near 10–30 kV for small parts; bump as needed |
| Ground rod & clamp | Completes circuit for transfer | Bright metal contact; scrape hooks often |
| Oven (dedicated) | Melts and cures the film | Parts must fit without touching walls or elements |
| Air supply with dryer | Keeps powder flow steady | Target clean, dry air; 5–10 cfm is plenty for most guns |
| Media blaster or sanding tools | Removes oxides and paint | Choose media that matches the alloy and finish goal |
| Degreaser & lint-free wipes | Strips oils | Final wipe before preheat |
| IR thermometer or probe | Reads part temperature | Always base cure time on metal temperature |
| DFT gauge | Measures film thickness | Most jobs land at 50–100 μm (2–4 mils) |
| PPE | Protects lungs, eyes, skin | Use a respirator rated for fine particulates |
Surface Prep That Makes Powder Stick
Finish quality starts with clean, reactive metal. Oil, dust, and oxides block adhesion and leave craters or fisheyes. Work in this order and don’t skip steps.
Strip And Clean
Remove paint and rust with blasting, a flap wheel, or a chemical stripper suitable for the base metal. Wash with a strong degreaser. Rinse and dry fully. Gloved hands only after this point.
Create A Profile
For steel and iron, light blasting to a uniform matte gives the best key. Aluminum likes a non-ferrous media or a conversion pretreatment. Stainless accepts a fine profile or a suitable etch. Aim for even texture.
Outgas Control
Preheat thick castings and porous alloys to drive off trapped volatiles. Let parts cool to your spray window. This reduces pinholes and bubbles during cure.
Grounding And Booth Setup
Good ground is the secret to fast, even coverage. Hang parts on clean steel hooks. Tie the rack to a dedicated rod. Check contact points often.
Test Your Ground
Use a megohmmeter, not a basic multimeter. The target is a very low resistance path from part to earth. Poor ground shows up as low transfer, orange peel, and rough edges.
Keep Air And Powder Dry
Moisture clumps powder and kills wraparound. Use a dryer on the airline and store powder in sealed tubs. Sift clumpy powder or bin it.
Choosing Powder And Color Systems
Select the chemistry for the duty cycle, not just the shade. Polyester handles outdoor use and daily wear. Epoxy bonds well and resists chemicals but can chalk outside. Hybrids split the difference for indoor items. Primers with zinc-rich content help with aggressive corrosion zones.
Gloss level alters the look and how dings show. High gloss pops but shows defects. Satin hides minor waves. Textures mask small surface marks and add grip. Metallic and candy shades need steady gun movement to keep flake even across faces and edges.
Read the TDS before you buy. Note cure window, film build range, storage limits, and any bend or impact guidance. Keep a binder of TDS sheets near the booth so settings and bake time stay consistent job to job.
Powder Coating Metal At Home: Step-By-Step
1) Hang, Mask, And Preheat
Thread hooks through holes or threaded points that can be chased later. Mask seats, threads, and bearing lands with silicone plugs or high-temp tape. For thick parts, warm to 50–70 °C so powder flows on contact.
2) Dial In The Gun
Start with low kV and low microamps. Hold the tip 15–25 cm from the surface. Keep the gun perpendicular on flats; sweep edges with quick passes to avoid build-ups.
3) Spray The First Pass
Coat edges, corners, and recesses first. Then load the broad faces. Aim for a thin, even cloud. If the cloud looks ropey, reduce flow. If it looks lazy, bump air a touch.
4) Flash And Check
Move the rack to the warm zone or a low oven set just below gel. Powder will gloss and level. Pull the rack and inspect under bright light. Touch thin spots right away.
5) Bake To The Film’s Schedule
Start timing only when the metal hits the specified temperature. Most polyesters cure in a window near 10 min at 180 °C, with shorter times at higher temperatures. Follow the product TDS without guesswork.
6) Cool, Handle, And Rework
Let the rack cool until the film hardens. Unhook parts on padded benches. If a flaw sneaks through, scuff the area, blow clean, and spot coat, then recure to the same schedule.
Film Thickness, Cure Windows, And Test Checks
Most decorative jobs land near 2–4 mils (50–100 μm). Heavy service can run thicker with the right powder grade. Measure DFT with a calibrated gauge on bare metal and record a few readings per side.
Low-temp powders and primers have different cure windows. Read the label. Some systems want a partial cure on the primer, then a full cure on the topcoat. Watch for yellowing on light colors if you push temperature too high.
Do quick checks after cool-down. Tape adhesion, a bend on scrap, and a solvent rub tell you if the cure is honest. Log results with part numbers and dates.
Material-Specific Notes
Carbon Steel And Mild Steel
These take a blast easily and hold a profile well. Remove mill scale for a smooth film. For outdoor parts, add a primer under your topcoat. Watch sharp corners. Round them lightly so film doesn’t thin on the edge.
Aluminum And Alloys
Degrease, rinse, and avoid steel media that can smear and cause dark specks. Conversion pretreatments help with adhesion and filiform corrosion. Many grades cool fast, so confirm that metal temperature has actually reached cure spec before you start timing.
Cast Iron And Porous Castings
These tend to trap oils and gas. Bake empty parts first, then cool to spray range. Choose powders labeled for outgas resistance when parts show stubborn pinholes. A light second pass after flash often evens the look.
Safety And Ventilation
Powder is fine particulate. Wear eye protection and a respirator. Keep sweep-up tools nearby. Ventilate the booth and keep the fan running after spraying stops so dust clears.
If you spray near flammables, follow fire codes for booth layout, interlocks, and housekeeping. A grounded system, clean filters, and spark control keep risk down.
Codes, Testing, And Reference Specs
For booth fire protection and layout requirements, see NFPA 33. For spray area ventilation rules, the OSHA 1910.107 standard sets baseline expectations. Use these as your shop’s guardrails.
When you need a formal adhesion check, run a tape test per your coating plan or customer spec. Keep a note in your traveler with the method and pass/fail.
Troubleshooting Powder Defects
Even with tight prep and clean gear, defects can pop up. The table below lists the common ones you’ll face, what triggers them, and how to fix each fast.
| Defect | Likely Cause | Fast Fix |
|---|---|---|
| Pinholes | Outgassing or trapped moisture | Prebake parts; switch to outgas-forgiving powder |
| Orange peel | High build or poor flow | Lower kV; reduce film; verify cure temp ramp |
| Thin edges | Poor wrap on corners | Reground hooks; precoat edges first |
| Fish eyes | Silicone/oil contamination | Strip, deep clean; ban silicone near booth |
| Blisters | Overbake or volatile residue | Shorten bake; improve degrease and rinse |
| Color shift | Over-temperature exposure | Follow the exact TDS schedule |
| Poor adhesion | Weak prep or undercure | Blast again; confirm time at part temperature |
Pro Moves That Raise Quality
Keep Hooks And Racks Bright
Scrape and replace contact points. Paint build-up kills ground and wastes powder. A shiny path to earth also reduces Faraday cage problems in tight corners.
Log Cure Profiles
Tape a thermocouple to a test coupon and ride it through the oven. Save the plot. If the center of a heavy casting lags, shift rack position or extend dwell so the whole part sees the right curve.
Use The Right Nozzle
Flat nozzles lay down smooth films on panels. Round cones reach spokes and recesses. Keep a spare diffuser; a nicked cap distorts the cloud and leaves stripes.
Switch Powders The Smart Way
Blow down the hopper, gun, and booth before color changes. Run a purge shot on a scrap panel to confirm the cloud is clean before you commit parts.
Budget, Layout, And Workflow
A small bench gun, a used electric oven, and a basic blast setup can handle brackets, guards, and trim. Keep the spray zone clean and separated from sanding. Hang a curtain to block dust. Place the rack, gun stand, and air control within easy reach so passes stay smooth.
Batch parts by color and cure window. Pre-stage masked items on one rack while another bakes. Label hooks with metal tags so you can track parts through prep, spray, and cure. That simple habit cuts rework.
Track powder use by weight. Weigh the hopper before and after a set of parts. Note film readings and cycle times. Those numbers help you quote better and spot waste from poor transfer or heavy film.
Quick Quality Checklist
Before Spray
Wipe test passes with a clean white cloth. Hooks are bright. Powder is dry and sifted. Air dryer is purged. Booth filter is clean.
During Spray
Cloud is even. Edges get a light pass first. Corners show wrap. Nozzles are free of powder cakes. Gun current stays stable.
After Cure
Metal temperature met spec. Film reads within range on flats and edges. Adhesion passes your shop test. Parts cool on padded racks to avoid dents.
Plan Your First Small Project
Pick a part with simple geometry. A brake lever, a flat bracket, or a set of test coupons works well. Run the full process once with that part. Take notes on gun settings, film readings, and bake time to metal temperature. Your second run will feel easy.
As your shop grows, add a better dryer, a sturdier rack system, and a dedicated curing oven. Keep your process sheet taped to the booth, and your results stay repeatable.