What Is Powder Coating?
Powder coating is a dry finishing process used to protect and colour aluminium products. Unlike wet paint, powder coating uses finely ground particles of pigment and resin that are electrostatically charged and sprayed onto the metal surface. The coated aluminium is then cured in an oven at around 200°C, which melts the powder into a smooth, hard, continuous film.
The result is a finish that is tougher, more uniform, and more durable than any liquid paint. It does not run, drip, or sag during application, and it bonds to the aluminium at a molecular level.
For aluminium window cills, flashings, and parapet cappings, powder coating is the industry standard finish. It provides colour, UV protection, and corrosion resistance in a single application.
Why Powder Coating Matters for Aluminium Cills
Aluminium is naturally corrosion-resistant. It forms a thin oxide layer when exposed to air, which protects the metal underneath. So why bother coating it at all?
Three reasons.
Colour. Raw aluminium is silver-grey. On a modern Irish home with anthracite windows and a cream render, a silver cill looks wrong. Powder coating lets you match any RAL colour to your windows, doors, fascia, and render.
UV resistance. Bare aluminium oxidises unevenly over time, developing a chalky, patchy appearance. Powder coating contains UV stabilisers that keep the colour consistent for decades.
Enhanced protection. While aluminium resists rust, it can pit and stain in aggressive environments. Coastal locations, industrial areas, and spots with heavy pollution all accelerate surface degradation. Powder coating adds a barrier that handles these conditions.
Every product on Cills.ie is powder-coated as standard. You choose your RAL colour during the ordering process and see a live preview before you confirm.
How the Powder Coating Process Works
Understanding the process helps you appreciate why quality varies between suppliers. Here is what happens to your aluminium cills before they reach your site.
Step 1. Pre-treatment
The aluminium is cleaned to remove oils, dirt, and the natural oxide layer. This is done through a chemical wash process, typically involving degreasing, acid etching, and a chrome-free conversion coating.
Pre-treatment is the most important step. If the surface is not perfectly clean, the powder will not adhere properly. Poor pre-treatment is the number one cause of coating failure, peeling, bubbling, and flaking.
Step 2. Powder application
The aluminium profiles are hung on a conveyor system and passed through a spray booth. Electrostatic spray guns give the powder particles a positive charge, while the aluminium is grounded. The charged particles are attracted to the metal surface and cling to it evenly.
A skilled operator adjusts the gun settings for different profile shapes. A flat window cill needs different settings than a complex bay cill with multiple angles. Getting even coverage on returns, drip edges, and upstands requires experience.
Step 3. Curing
The coated profiles enter a curing oven at 180-200°C for 15-20 minutes. The heat causes the powder particles to melt, flow together, and chemically crosslink into a continuous film.
The curing temperature and time must be precise. Under-cured coatings are soft and scratch easily. Over-cured coatings become brittle and can crack during handling or installation.
Step 4. Quality inspection
After cooling, each piece is inspected for thickness, adhesion, and appearance. Film thickness is measured with a gauge, checking that it falls within the specified range. Adhesion is tested using cross-hatch and bend tests. Colour is verified against the RAL standard.
Film Thickness. Why It Matters
Powder coating thickness is measured in microns (μm). One micron is one thousandth of a millimetre. The standard for architectural aluminium in Ireland is 60-80 microns.
Here is why thickness matters.
Too thin (under 50 microns): The coating does not provide adequate UV protection. Colour fades faster. Corrosion resistance is reduced. Pin-holes in the film let moisture reach the aluminium.
Correct range (60-80 microns): Full colour stability, UV protection, and corrosion resistance. This is what you should expect from any reputable supplier.
Marine grade (80-120 microns): For properties within 5km of the Irish coast, thicker coatings are essential. Salt air is aggressive and accelerates coating breakdown. Marine-grade thickness extends the service life significantly.
Too thick (over 120 microns): Excessive thickness can cause orange peel texture, poor edge coverage, and brittleness. More is not always better.
When ordering from Cills.ie, standard coating is 60-80 microns. Marine-grade options are available for coastal projects.
RAL Colours for Irish Projects
The RAL colour system is the European standard for colour matching. It contains over 200 defined colours, each with a unique code. This means a cill powder-coated in RAL 7016 in Dublin will be the exact same shade as one coated in RAL 7016 in Munich.
Most Popular RAL Colours for Aluminium Cills in Ireland
Based on orders through Cills.ie, here are the colours Irish customers choose most.
RAL 7016 Anthracite Grey accounts for roughly 40% of all orders. It matches the most popular window frame colour in Ireland and works well with both light and dark renders.
RAL 9005 Jet Black is the second most popular. Clean, modern, and striking against white or cream walls.
RAL 7015 Slate Grey offers a softer alternative to anthracite. Popular on heritage-style retrofits where a less industrial look is preferred.
RAL 9003 Signal White suits traditional homes and bright, clean aesthetics. It shows dirt more than darker colours but is easy to clean.
RAL 7032 Pebble Grey and RAL 7044 Silk Grey are warm neutrals that complement natural stone and timber finishes.
RAL 8028 Terra Brown is chosen for rural properties where the cills need to blend with natural surroundings.
You can preview any RAL colour on your cills before ordering. The Cills.ie colour selector shows a live visual of your chosen finish.
Powder Coating vs Anodising. What Is the Difference?
Some aluminium products are anodised rather than powder-coated. Anodising is an electrochemical process that thickens the natural oxide layer on aluminium, creating a hard, transparent finish.
Anodising advantages: Extremely hard surface. Does not chip or peel. Metallic appearance preserved.
Anodising disadvantages: Limited colour options (silver, bronze, black, gold). Cannot match RAL colours. Repairs are difficult. Cost is higher for custom colours.
Powder coating advantages: Any RAL colour available. Easy to repair minor damage with touch-up paint. Lower cost for custom colours. Better UV resistance.
Powder coating disadvantages: Can chip if hit hard. Slightly less scratch-resistant than anodised finishes.
For architectural applications in Ireland, where colour matching to windows and renders is essential, powder coating is the clear choice. Anodising is better suited to curtain walling and commercial glazing systems where a metallic finish is desired.
Durability in Irish Weather
Ireland's climate is tough on building materials. High rainfall, strong winds, salt air on the coast, and frequent temperature changes all test the durability of external finishes.
Quality powder coating handles all of this.
Rain. The cured coating is completely waterproof. Water beads on the surface and runs off. There is no absorption, swelling, or softening.
UV. Irish UV levels are lower than southern Europe, but cumulative exposure still matters. Polyester powder coatings used on architectural aluminium contain UV stabilisers that maintain colour for 25-30 years.
Salt. Coastal environments require marine-grade coatings. Standard coatings can show signs of degradation within 10-15 years near the coast. Marine-grade coatings with 80-120 micron thickness and enhanced pre-treatment extend this to 25+ years.
Temperature. Powder coatings flex with the aluminium as it expands and contracts through temperature cycles. A cill in full sun can reach 60°C on a summer day and drop below freezing on a winter night. Quality coatings accommodate this movement without cracking.
Common Powder Coating Problems and How to Avoid Them
Not all powder coating is equal. Here are the problems that indicate poor quality or improper application.
Orange peel texture
The surface looks bumpy, like the skin of an orange. Caused by incorrect spray settings, wrong powder particle size, or inadequate oven temperature. A well-coated cill should feel smooth to the touch.
Colour inconsistency
Different pieces in the same order appear slightly different shades. This happens when powder batches are not consistent, or when oven temperature varies across a batch. Reputable coaters use powder from the same batch for each order and calibrate ovens regularly.
Peeling or flaking
The coating lifts away from the aluminium. This is almost always a pre-treatment failure. The surface was not clean enough for the powder to bond properly. This is the most serious defect and means the coating will continue to fail.
Pin-holes
Tiny holes in the coating expose the aluminium underneath. Usually caused by gas trapped in the aluminium escaping during curing. Proper degassing before coating eliminates this issue.
How Cills.ie avoids these problems
Every piece is pre-treated in a multi-stage chemical wash. Coating thickness is verified on each batch. Ovens are calibrated weekly. And finished products are inspected before dispatch.
Powder Coating and External Wall Insulation
For external wall insulation projects in Ireland, the powder-coated finish on your aluminium cills is the first thing people see. The cills sit proud of the render, framing every window. Any imperfection in the finish is visible.
This is why getting the colour right matters. A cill in RAL 7016 that does not quite match the RAL 7016 window frames is noticeable from the street. It looks like an afterthought rather than a coordinated design.
Cills.ie uses verified RAL colour standards. Your cills will match your windows, your flashings, your cappings, and any other powder-coated elements on the project.
For complex projects with bay window cills or multi-segment designs, all pieces are coated together from the same powder batch to ensure perfect colour consistency across the installation.
How to Order Powder-Coated Aluminium Cills
The traditional way involved phone calls, faxes, and guesswork about colours. You would describe what you wanted, the fabricator would interpret it, and you would hope the result matched your expectations.
Cills.ie has replaced that process with a digital ordering system.
Enter your dimensions. Width, projection, upstand height, and end cap details. The system validates your inputs and flags any issues.
Choose your RAL colour. Browse popular colours or enter any RAL code. See a live preview of your chosen finish.
Review your order. A 3D preview shows exactly what you are getting. Check every dimension and detail before confirming.
Track your order. From fabrication through powder coating to dispatch, you can see where your cills are in the process.
No phone calls. No misunderstandings. No colour surprises on delivery day.
Maintaining Powder-Coated Aluminium
Powder-coated aluminium is low maintenance, but not zero maintenance. A simple cleaning routine keeps your cills looking sharp.
Routine cleaning. Wash with warm soapy water and a soft cloth twice a year. This removes dirt, pollen, and atmospheric deposits before they build up.
Avoid abrasives. Never use wire wool, scouring pads, or abrasive cleaners. These scratch the coating and create entry points for moisture.
Check sealant joints. While cleaning, inspect the silicone sealant where cills meet the render and window frames. Reseal if you see cracks or gaps.
Touch up damage. If the coating is chipped or scratched, clean the area and apply a RAL-matched touch-up paint. This prevents moisture reaching the aluminium.
For coastal properties, increase cleaning frequency to four times a year. Salt deposits accelerate coating degradation if left in place.
The Cost of Powder Coating
Powder coating typically adds 15-25% to the cost of raw aluminium products. For a standard window cill, this means a few euros per piece. Considering the decades of protection and the aesthetic value, it represents excellent value.
Marine-grade coating costs 20-30% more than standard coating. For coastal projects, this is money well spent.
Compared to alternatives like painting aluminium on site (which peels within years) or leaving it uncoated (which looks poor within months), factory-applied powder coating is the most cost-effective long-term solution.
Ready to order powder-coated aluminium cills? Cills.ie lets you choose any RAL colour, see a live preview, and order in minutes. Custom sizing, factory-fitted end caps, and nationwide delivery included.
Powder Coating Aluminium Cills, Flashings and Cappings in Ireland
A practical guide to powder coating aluminium window cills, flashings and cappings for Irish retrofit and new build projects.
Cills.ie Team
Powder Coating Guide
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