PL
ENPowder coating is exceptionally hard and hard-wearing, but it is not indestructible. A chip picked up in transit, a scratch along an edge, a spot of rust under the coating - damage like this happens both in production and after years of service. The question is usually the same: can this be touched up locally, or does the whole coating have to come off and be redone from scratch? The answer depends on the type of damage, where the part is in service and how much appearance matters. We run through every repair method worth considering and show where each one earns its place.
What decides the repair method? Assess the damage first
Not every kind of damage calls for the same approach. Before you reach for any method, check 3 things: how deep the damage goes, how large an area it covers and whether corrosion has already set in underneath. Those three answers decide whether a touch-up will do or whether the part has to go back to the coating shop.
Surface damage
Dulling and light scratches that don't reach the metal. The coating is still protecting the substrate. This is mainly about appearance, and the repair is the simplest.
Chips down to the metal
The coating has come off in one spot and bare metal is showing. The substrate is exposed, so time matters. Left unprotected, that spot will soon start to rust.
Corrosion under the coating
Rust creeps under the paint film and lifts it from below (under-film corrosion). This is the most serious case - painting over it will do nothing unless you remove the source.
Watch out for under-film corrosion. If the coating around the damage is bulging or can be lifted with a fingernail, corrosion is already at work under the film. Painting over the top without removing the rust will only hide the problem for a few weeks, and the blister will come back bigger.
3 ways to repair a powder coating
In practice there are 3 approaches. They differ in the amount of work involved, how long the result lasts and how well the repair blends in with the rest of the surface. They are listed from the simplest to the most labour-intensive.
Method 1 - touch-up with wet paint
The quickest method for individual chips and scratches. The damaged spot is cleaned of loose coating and any rust, degreased and made good with a colour-matched wet paint. The options are:
- a touch-up pen or brush bottle - for small spots,
- aerosol paint - for larger but still localised damage,
- two-pack paint applied by spray gun - when the repair needs to be more durable.
There is one drawback, but it matters: a wet-paint repair will never reach the same hardness and resistance as a powder coating. It works as protection and a cosmetic fix, not as a full restoration of the film.
Method 2 - recoating the whole part with powder
When there is a lot of damage, or a uniform look matters, the part is cleaned and goes through the powder coating process again. The new layer can be applied over the old one (overcoating) if the old coating is sound, fully cured, degreased and lightly abraded to give a key. This gives a factory finish, because the whole surface goes through the same process.
There is one purely practical catch: the part has to fit in the oven and withstand baking at 160-200°C. For oversized or heat-sensitive parts this option is out.
Method 3 - full strip and recoat
The most labour-intensive option, necessary where there is extensive corrosion, flaking old paint or a substrate that was poorly prepared in the first place. The old coating is stripped completely, using one of three methods:
- thermally - in a burn-off (pyrolysis) oven, for steel parts; the coating burns off leaving an ash residue that is then blasted or washed off,
- mechanically - grit or shot blasting with abrasive media,
- chemically - immersion in a chemical strip tank that dissolves the coating (the route for aluminium and thin-gauge parts).
Once the coating is off, the part goes through full surface preparation and powder coating as if it were new. This gives the most durable result, because we are fixing the cause, not the effect.
Read also: The most common problems in powder coating and how to solve them
Touch-up or recoat? A comparison
Choosing between a local repair and a full recoat is always a trade-off between time, cost and durability. The table sets out when to reach for each method.
| Method | When to use it | Durability of the repair |
|---|---|---|
| Wet-paint touch-up | Individual chips and scratches, inconspicuous spots, urgent protection of the metal | Limited - weaker than a powder coating |
| Powder recoat | Multiple areas of damage, uniform look required, part fits in the oven | High - close to a factory finish |
| Full strip and recoat | Extensive corrosion, flaking old paint, defective substrate | Highest - removes the cause of the damage |
The rule is simple: the deeper the damage goes and the larger the area it covers, the more serious the method. Touching up a scratch with rust underneath is treating the symptom - the corrosion carries on working. Stripping the whole coating over a single scratch means paying over the odds and several days of downtime.
Touch-up repair step by step
A wet-paint touch-up is the repair people most often do themselves. Done properly, it will last for years, as long as you don't skip the preparation. Here is the sequence that works.
- Clean the damaged spot - remove loose flakes of coating and, if there is rust, sand it back to sound metal with fine abrasive paper,
- Degrease the surface - use panel wipe or isopropyl alcohol; grease and dust kill adhesion,
- Protect the metal - where the chip goes down to the substrate, apply a thin coat of anti-corrosion primer to the bare metal,
- Apply the paint in thin coats - several light passes give a better result than one heavy coat, which will run,
- Match the colour and gloss - check the RAL number and gloss level of the original coating, so the repair doesn't stand out as a patch.
Colour matching
If you know the RAL number and gloss level of the original coating, the touch-up will be almost invisible. If you don't have the number, try the touch-up paint on a test patch in an inconspicuous spot before you tackle the visible surface.
Read also: Surface preparation for powder coating - stages, mistakes and best practice
What are the most common repair mistakes, and how do you avoid them?
Most failed repairs come down to rushing the preparation stage. Here are the situations that come up most often, and what to do instead.
Painting over rust
Painting over a corrosion spot without removing it. The rust carries on working under the paint, and after a few weeks the coating cracks and comes away in flakes.
Take the rust back to sound metal
Sand or blast the corrosion away, and only then prime and paint. The repair holds for as long as there is no rust underneath.
Skipped degreasing
Paint won't key to a greasy or dusty surface. The touch-up comes off at the first knock or change in temperature.
Always degrease before painting
Panel wipe or isopropyl alcohol and a clean, lint-free cloth. It's 30 seconds of work that decides whether the repair sticks.
Too heavy a coat in one go
One heavy pass with an aerosol will run, wrinkle and take an age to dry. The result looks worse than the damage itself.
Several thin coats
Apply lightly, allowing each coat to flash off. The coats build up an even, opaque colour with no runs.
When is it better to leave the repair to a coating shop?
A wet-paint touch-up in the garage makes sense for minor damage. There are cases, though, where a DIY repair is a waste of material and the part will have to go to a professional powder coater anyway.
- corrosion covers a larger area or keeps coming back despite touch-ups,
- you want a uniform, factory finish with no visible patches,
- the part works outdoors or in an environment with a high corrosivity category (ISO 12944 C4-C5),
- the old coating is flaking over a large area and needs stripping completely.
At the coating shop the part will go through full substrate preparation and baking in an oven, which no home touch-up can replace. A powder repair restores the coating's original durability rather than just masking the damage. Choosing the right powder, RAL number and film thickness is then down to the coating shop.
Recoating a damaged part? We'll match the coating
When the repair means recoating, the whole result depends on matching the original: colour, gloss and texture. We can reproduce a coating in any RAL, Pantone or NCS shade, with the right gloss and texture, so the recoated part doesn’t stand out from the rest of the surface. We’ll send samples before you order – you can check the match on your own part.
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