N NorthlineCoating
(616) 452-8817 Get a Quote

Six stages.
Same line for every part.
No shortcuts.

Powder coating looks simple from the outside: spray powder on metal, bake it, ship it. In practice, ninety percent of coating failures trace back to something that happened before the powder ever touched the part. This page walks through exactly what we do — and why each stage matters.

Start a Project → Jump to step 1
Overview

The process isn't
the powder. It's
everything around it.

The single most common reason a powder coat fails is bad preparation — not bad powder. A premium polyester applied over a poorly prepared substrate will fail faster than an inexpensive epoxy applied over a properly pretreated one. That's the entire reason we built our process around pretreatment, film-thickness verification, and lot traceability rather than speed.

Every job that enters our shop — whether it's a single bracket or a ten-thousand-piece production run — goes through the same six stages. There's no "quick line" for small jobs. There's no skipping pretreatment when the customer is in a hurry. There's no partial cure when the ovens are backed up.

The steps below are what happens to your parts from the moment they arrive at 1120 Burton Street to the moment they ship out. We're not hiding anything — this is the same process we walk customers through on facility tours.

01
Stage One

Intake & Inspection

Every lot that arrives at our loading dock is logged, photographed, and inspected before it goes anywhere near the coating floor. We look for dents, deep scratches, weld spatter, mill scale, and any existing finish that will need to come off. Anything we find gets documented and, if it affects the quote or the timeline, we call you before we touch the part.

This stage exists because we'd rather have an uncomfortable phone call on day one than ship parts that fail QC on day five because of a defect that was already there when they arrived. Customers get a copy of the inspection report with their job — it's a protection for both sides.

Documented Per-part photos, defect log, lot number
Time on floor 15–45 minutes depending on lot size
Customer communication Same-day call if issues found
02
Stage Two

Blast & Pretreatment

Pretreatment is the stage that decides whether your coating lasts three years or fifteen. We run two pretreatment paths depending on the substrate and the coating spec, and on some jobs we do both.

Media blasting uses aluminum oxide abrasive to strip existing finishes, remove mill scale and rust, and create a surface profile for mechanical adhesion. This is the default for parts with old coatings, heavy rust, or weld contamination.

Chemical pretreatment runs parts through a 7-stage iron phosphate line: alkaline clean, rinse, rinse, iron phosphate conversion coating, rinse, rinse, DI rinse, and dry-off. The phosphate layer chemically bonds to the steel and gives the powder a conversion-coated surface to adhere to. This is what we use on most clean steel and cast iron parts.

Aluminum gets a chromate conversion pretreatment instead of phosphate — the chemistry is different because aluminum oxidizes differently than steel.

Blasting media Aluminum oxide, 80–120 grit
Phosphate stages 7-stage iron phosphate, DI rinse
Aluminum pretreatment Chromate conversion or chrome-free
03
Stage Three

Masking

Masking is the stage most customers never see and rarely think about — until they get parts back with powder in the threads, or a hub bore that no longer accepts a bearing. We mask every surface that needs to stay bare: threaded holes, machined bores, electrical contact points, hub faces, and any surface where dimensional tolerance matters.

We use high-temperature silicone plugs, caps, and tape — not standard masking tape. Standard tape breaks down in the 400°F cure cycle, leaves adhesive residue, and shrinks during cure. Silicone masking survives the full cycle without leaving anything behind.

For complex parts with many masked features, we build a masking jig that holds all the plugs in place and can be reused across a production run. It's slower on the first part and much faster on every part after it.

Masking materials High-temp silicone plugs, caps, and tape
Typical masked surfaces Threads, bores, mating faces, contact points
Production runs Reusable masking fixtures built per part
04
Stage Four

Powder Application

Parts are grounded on a rack and moved into the spray booth. Electrostatic spray guns apply a high-voltage charge to the powder particles as they leave the nozzle, and the charged particles are attracted to the grounded part. The powder sticks to the part through electrostatic attraction — nothing is wet, nothing is solvent-based, and nothing drips.

We run Nordson HDLV pumps and guns across two application cells. Cell 1 handles heavy-build industrial and architectural work with automated reciprocators. Cell 2 handles smaller and more detailed work — automotive, custom, and short-run production — with manual application and touch-up.

Film thickness is monitored wet and cured. Wet thickness is checked visually against a target profile; cured thickness is verified with an electronic gauge after the part exits the oven. Parts outside the target range get recoated — not shipped and apologized for later.

Equipment Nordson HDLV pumps and electrostatic guns
Cells Cell 1 automated · Cell 2 manual + touch-up
Typical film build 2–4 mil standard · up to 15 mil heavy-build
05
Stage Five

Curing

Curing is where the powder becomes a coating. Parts move from the spray booth into batch ovens held at the powder manufacturer's specified cure temperature — usually 350°F to 400°F — for a full dwell time that's also specified by the powder maker. During this stage, the powder particles melt, flow into a continuous film, and chemically cross-link into a hard, durable finish.

Cure temperature and dwell time are not flexible. Powder that cures at 380°F for 10 minutes and powder that cures at 380°F for 6 minutes will look identical immediately after they come out of the oven and behave completely differently six months later. Under-cured powder chips, fades, and loses adhesion. We log every oven cycle — time in, time at temp, time out — and hold parts at full cure even when the schedule is tight.

For heat-sensitive parts (pre-assembled components, electronics enclosures, and some aluminum substrates), we run low-temperature powders that cure at 250–300°F. Low-temp cure takes longer but allows parts to be coated that would otherwise be disassembled or impossible.

Standard cure 350°F – 400°F · full dwell per manufacturer spec
Low-temp cure 250°F – 300°F · extended dwell
Logging Time-in, time-at-temp, time-out per cycle
06
Stage Six

QC & Release

After cure, parts go through final inspection before they're released for shipping. The inspection covers four things: film thickness, visual appearance, adhesion, and masking integrity.

Film thickness is verified with an electronic dry-film gauge. We measure multiple points per rack and compare against the target range. Out-of-spec parts get recoated.

Visual inspection happens under controlled lighting. We look for runs, sags, orange peel, contamination, and coverage gaps — the kind of defects that a customer will see immediately and that pass unnoticed in a dim shop.

Adhesion is spot-checked on sacrificial or test parts using a cross-hatch or impact test. Not every part gets destructive testing, but every lot gets a verification that the coating is properly bonded.

Masking integrity means we confirm every masked surface is actually bare, every plug has been removed, and no residual silicone or tape adhesive is left on the part.

Parts that pass inspection are packed with foam corner protection and non-abrasive interleaving. Every shipment leaves with a certificate of conformance documenting powder batch, thickness readings, and cure log.

Thickness check Electronic gauge, multiple points per rack
Adhesion check Cross-hatch or impact test per lot
Documentation Certificate of conformance per shipment
What's different here

Four things
other shops skip.

Most of the difference between a coater and a good coater comes down to what they do when nobody's watching. These are the four things we refuse to cut corners on.

01

We refuse to skip pretreatment

Some shops "spot-pretreat" parts — wire-brush the visible surfaces and coat the rest as-is. We don't. Every part goes through the full blast or chemical pretreatment line, even when it's slower, even when the customer doesn't ask.

02

We hold full cure, always

When the ovens are backed up and the schedule is tight, the temptation is to pull parts early. We don't. Under-cured powder looks fine for six weeks and then fails. Cure logs are archived for every batch.

03

We document everything

Powder batch, cure log, thickness readings, operator initials, QC sign-off — all recorded for every lot. If something goes wrong, we can trace it to the specific hour, oven cycle, and person. That's how you fix problems instead of guessing.

04

We coat ten-piece jobs like production

There's no "custom line" with a shorter cure or looser tolerances. A single-part job goes through the same six stages as a ten-thousand-piece production run. The only thing that changes is the rack setup and masking approach.

Typical timeline

What a normal job
actually looks like.

  1. Day 0

    Quote & Approval

    Send us the drawings or photos and quantities. We return a firm quote within one business day. You approve, ship the parts, and we confirm arrival date.

  2. Day 1

    Intake & Inspection

    Parts logged, photographed, and inspected. Any issues flagged the same day. If the job needs a color match, this is when the test panel gets ordered or created.

  3. Day 2

    Blast & Pretreatment

    Full pretreatment cycle. Depending on the substrate and system, this stage takes most of a working day for a standard lot.

  4. Day 3

    Masking & Coating

    Masking setup in the morning, powder application through the afternoon. Cure cycles typically run overnight to give full dwell time at temperature.

  5. Day 4

    QC & Release

    Final inspection, thickness verification, documentation, and packing. Parts staged for shipment or customer pickup.

  6. Day 5

    Shipment

    Standard production job ships on day five for local customers and pickup orders. Freight shipments depend on carrier schedules.

Process FAQ

Questions about
how we work.

Can I tour the shop and see the process in person?

Yes. We welcome facility tours for fabricators, contractors, engineers, and designers who are evaluating a coater for ongoing work. Tours typically take 30–45 minutes and cover the full line from intake to shipping. Call Maria directly at (616) 452-8817 to schedule.

What happens if my parts need structural repair before coating?

We'll document the damage during intake inspection and call you the same day with photos. If it's minor cosmetic repair (small dents, curb rash on wheels), we can usually fix it and quote the repair into the job. If it's structural damage that affects how the part will perform, we'll advise you before touching it — sometimes the right answer is that the part shouldn't be recoated.

Do you strip existing powder or paint before recoating?

Yes, always. Coating over an existing finish is the most common cause of premature powder coat failure. We strip by blasting, chemical, or burn-off depending on the substrate and the old coating. This is built into our quotes as a standard step, not an optional line item.

How do you handle small parts like brackets and clips?

Small parts get racked on wire fixtures that hold them individually. Loose parts in a basket don't get the same coverage and don't hold the charge properly. For production runs of small parts, we build reusable rack setups that hold every piece in the same orientation, which keeps film build consistent across the run.

Can you coat heat-sensitive parts?

Yes. We run low-temperature powders that cure at 250–300°F for parts that can't survive a standard 400°F cure. This includes pre-assembled components, aluminum substrates with specific alloy considerations, and enclosures with internal electrical components. Low-temp cure requires a longer dwell time, so it adds a day to the schedule.

What documentation comes with the parts?

Every shipment includes a certificate of conformance documenting the powder manufacturer and batch, cure log (times and temperatures), film thickness readings per rack, operator initials, and QC sign-off. For work requiring additional documentation (defense, medical, aerospace-adjacent), we can add chemical resistance testing results, salt-spray hours, and per-part traceability.

How do you handle recoating if a part fails QC?

Parts that fail QC get stripped back to bare metal, re-blasted, and recoated from scratch. We don't attempt to "patch" a failed coating — it doesn't work and it just creates problems downstream. The recoated part goes through the same six stages as the original, and we cover the cost of the redo.

Can you rush a job through the line?

Sometimes, if the line has capacity. Rush service is available at a premium and typically gets a job through in 48 hours instead of five business days. The six stages stay the same — nothing is skipped — but scheduling priority and oven cycles are adjusted. Call us before shipping if you need rush service.

Start your project

See the process
in person.

If you're evaluating coaters for ongoing production work, schedule a facility tour. We'll walk you through the line, show you the pretreat and oven equipment, and answer any technical questions you have about how we'd handle your specific parts.

Request a Quote → Call (616) 452-8817