Powder coating
A powder applied electrostatically is cured in an oven. Tough and attractive, it suits steel, aluminium and galvanised steel, with a wide choice of RAL colours and matt, satin or textured finishes.
Expertise
Surface treatment subcontracting
Painting, powder coating, anodising, galvanising, zinc plating: describe your parts and compare quotes from applicators.
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Surface treatment protects a part against corrosion, wear or chemical attack, or gives it the finish you want: colour, gloss, texture. It is often left until last in a project, yet it affects the choice of material, the final tolerances and the schedule. A poor choice costs you in rework, in parts that rust, or in fits that no longer assemble.
Processes fall into a few main families. Organic coatings include liquid paint, powder coating (powder paint cured in an oven) and cataphoresis (e-coating). Metallic coatings deposit or convert a metal on the surface: hot-dip galvanising, electro-galvanising, nickel plating, chrome plating. Conversion treatments, such as aluminium anodising or phosphating, transform the surface layer. Mechanical preparations (sandblasting, shot blasting, micro-bead blasting) prepare the surface or give it a particular look.
Choosing an applicator therefore means matching the process to the material, the use and the size of the part. This page covers the main treatments, their constraints (dimensions, masking, racking), the reference standards and the information to provide so that quotes can be compared.
Common services
Industrial liquid paint
Primer, intermediate coats and a spray-applied topcoat, for large parts, structures or special colours. Systems are chosen according to how corrosive the environment is.
Aluminium anodising
An oxide layer forms deep in the surface: it protects against corrosion, hardens the surface and can be coloured. Hard anodising is reserved for parts subject to friction and wear.
Hot-dip galvanising
Steel parts are immersed in a bath of molten zinc, giving thick, long-lasting protection for outdoor structures, guardrails or pylons.
Zinc plating and electrolytic treatments
Electrolytic zinc plating deposits a thin layer of zinc, passivated in various colours, on fasteners and small parts. Nickel plating and chrome plating are used for wear resistance or decorative finishes.
Sandblasting, shot blasting and micro-bead blasting
These preparations remove rust and mill scale, create the roughness that makes paint adhere, or give aluminium and stainless steel a uniform matt finish.
Passivation and electropolishing of stainless steel
An acid bath dissolves free iron and restores the passive layer of stainless steel after welding or machining; electropolishing also smooths the surface for hygienic uses.
Materials worked
Structural and engineering steelGalvanised or pre-coated steelAluminium and aluminium alloys (anodising, powder coating)Stainless steel (passivation, electropolishing, blasting)Cast iron (paint and treatments suited to its porosity)Brass and copper (nickel plating, protective lacquer)Mixed parts in metal and plastic or wood (liquid paint)Fasteners and small bulk parts (barrel zinc plating)
Common applications
- Mechanical parts to be protected against corrosion
- Outdoor steel structures and metalwork
- Housings, covers and casings in the manufacturer’s colour
- Machined aluminium parts with a decorative or wear-resistant finish
- Fasteners, fixings and small series parts
- Stainless steel equipment for food processing and medical use
- Metal furniture and light fittings
- Tooling and parts needing high wear resistance
What affects the price
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1
Process and level of protection
A standard powder coating, a hard anodising and a hot-dip galvanising are not priced the same way. The number of coats and the target thickness affect the price.
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2
Surface area and weight
Depending on the process, the price is quoted per square metre, per kilo or per part. Large parts take up space in the oven or bath and reduce the day’s capacity.
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3
Surface preparation
Degreasing, stripping, blasting, filling, sanding: the initial condition of the part determines the preparatory work, which is sometimes longer than the application itself.
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4
Masking and racking
Threaded holes, bores and bearing surfaces to be preserved are masked by hand, which adds time. Racking points leave a mark: plan them in a non-visible area.
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5
Special colours and finishes
An off-catalogue colour, a textured finish, a multi-coat system or a colour change in the booth leads to surcharges.
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6
Batch size and minimum charge
Many applicators set a minimum per batch, because tanks, ovens and booths must be full to be profitable. Grouping your parts into a single shipment helps bring the cost down.
Tips for a successful request
Post a request- State the exact material of each part, because aluminium, stainless steel and steel are not treated in the same way.
- Specify the process you want and the level of protection required: operating environment, expected service life, salt spray resistance.
- Give the colours (RAL reference or sample), the finish (matt, satin, gloss, textured) and the surfaces where appearance matters most.
- Mark on the drawing the areas to be masked (threaded holes, bores, electrical contacts) and the acceptable racking points.
- Provide the maximum dimensions and weight of the parts, as well as the quantity and delivery rate.
- Ask for the inspections and certificates you need: coating thickness, adhesion, salt spray resistance, compliance with a standard.
Choosing the right treatment for the material and the environment
For steel used outdoors, hot-dip galvanising is the benchmark for lasting protection: the molten zinc forms a thick layer, from a few tens up to around a hundred micrometres depending on the thickness of the part (standard EN ISO 1461), which protects even when scratched. It can be combined with paint to form a “duplex” system, which lasts even longer and can be colour-matched. Very thin or complex parts can distort in the heat of the bath; hollow sections must be fitted with vent and drain holes.
For aluminium, anodising creates a layer integrated into the metal, which does not flake. A decorative or protective layer typically measures a few micrometres to around twenty, and hard anodising more. It grows partly into the metal and partly outwards, which changes the dimensions slightly. Powder coating aluminium is the alternative when a precise colour or a thick finish is wanted.
For small mechanical parts, electrolytic zinc plating with passivation offers moderate protection at low cost. For very hard steels, the risk of hydrogen embrittlement calls for a baking (de-embrittlement) treatment after plating: tell the supplier the mechanical strength of the part. For stainless steel, passivation restores the surface after welding or machining.
The corrosivity categories of standard ISO 12944 (from C1, dry indoor, to C5, very aggressive industrial or marine atmosphere) help define the paint system for a structure. Our guide to surface treatment of metals goes deeper into these choices.
Tolerances, masking and racking: the preparation pitfalls
A coating adds material. A powder coating generally measures around 60 to 100 micrometres per face, enough to block a close-fit bore or a tight thread. You must therefore either mask these areas or allow for adjusted dimensions before treatment, and say so on the drawing. Anodising also changes dimensions, more so the thicker the layer.
Masking requires manual work (plugs, tapes, peelable lacquer) that is priced per part. To limit costs, group the areas concerned, avoid deep bores that need protecting and mention it in the request. Racking is another point: to treat a part, the applicator hangs it on a hook or holds it by an electrical contact, which leaves an uncoated spot. Agree it with them, away from visible surfaces.
Finally, think about the order of operations. A machined, welded or bent part is generally treated last. If a heat treatment is planned, it often comes before the surface treatment. Coordinate everything with your machining or welding and fabrication workshop to avoid back-and-forth, and plan an inspection after coating if dimensions are critical.
Standards, tests and regulations to know about
The durability of a coating is checked through standardised tests. The most common is the neutral salt spray test (standard ISO 9227), expressed in hours of resistance before corrosion appears: it allows systems to be compared without exactly reproducing real-life conditions. Coating thickness, adhesion (by cross-cut or pull-off), gloss and colour are also measured.
Some sectors have labels that guarantee the quality of an application: in construction, labels exist for powder coating and anodising of architectural aluminium. Ask the applicator which ones they hold, if your specification requires them.
Regulations also restrict certain substances. Hexavalent chromium compounds, used in older passivation and chrome-plating processes, are tightly controlled by European regulations (REACH, RoHS): many applicators now offer trivalent chromium alternatives. For parts intended for food contact or medical use, state the requirements in your request from the outset.
For an effective request on Meaflow, group all the parts to be treated in a single request, with material, process and level of protection: applicators find their way around faster, and you compare their minimum charges, lead times and included inspections. Posting your parts list takes only a few minutes.
Suppliers: surface treatment
Guides to go further
Anodising, powder coating, zinc plating: choosing a surface treatment
Anodising, powder paint, zinc, passivation, nickel, chrome: the strengths and limits of each treatment, their effect on dimensions and how to specify it in a request.
Writing a manufacturing specification: method and template
What a workshop needs to know to quote and make your part: a method in a few points, a ready-to-copy template and common mistakes to avoid.
How to Write a Subcontracting Quote That Stands Out
Read the brief, set out a credible price and lead time, include the right details and stand out from other workshops: a step-by-step method.
Related expertise
CNC machining
Milling, turning, 3- to 5-axis machining centres
Welding & boilermaking
TIG, MIG, structures, tanks, metalwork
Sheet metalwork & cutting
Laser, plasma and waterjet cutting, bending
Inspection & metrology
Dimensional inspection, NDT, reports
Frequently asked questions
A question not answered here? Visit the help centre or write to us.
How much does powder coating or anodising cost?
The price depends on the process, the surface area or weight, the preparation, the masking, the colour and the batch size. Most applicators apply a minimum charge per batch, which weighs on small runs. To compare quotes, send the list of parts with their dimensions, material, finish and the areas to be masked.
Which treatment should I choose to protect against rust?
For outdoor steel, hot-dip galvanising or a paint system suited to how corrosive the location is. For small parts, electrolytic zinc plating with passivation. Aluminium and stainless steel resist better by nature: their treatment is mainly about appearance or wear. The applicator will advise you according to the operating environment.
What is the lead time for a surface treatment?
A standard powder coating or zinc plating can be done in a few days, whereas preparation, multiple coats or galvanising on a collection round can push the lead time to a week or more. Each trip between workshops lengthens the schedule. State the date you need and whether it is firm so that applicators can adapt their planning.
Does a surface treatment change the dimensions of the part?
Yes: every coating adds thickness. A powder coating adds around 60 to 100 micrometres per face, and anodising also changes dimensions, to a lesser extent. For a close-fit bore or a thread, plan for masking or an adjusted dimension before treatment, and show them on your drawing.
Can a single part be treated?
It is possible with some applicators, but the minimum charge often makes it uneconomic for one-offs. Group your parts into a single batch, or team up with another order. Some small paint or blasting workshops are more willing to take one-off parts and restorations.
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