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Powder Coating vs Wet Spraying Signage Components

Powder Coating Vs Wet Spraying Signage Components

Why this comparison matters

In the signage industry, finishes are often chosen late in the process — sometimes almost as an afterthought. However, the coating method used on profiles, trays, folded panels and fabricated components has a major impact on durability, appearance, compliance, cost, and long-term performance.

Two technologies dominate: powder coating and wet spraying (liquid paint systems). Both are widely used in UK manufacturing, but they solve different problems and suit different applications. This guide explains how each process works, where it performs best, where it can fail, and how to choose the right option for your project.

At a glance: the short answer

If you want a durable, outdoor-ready finish with excellent corrosion resistance, consistent colour, and low environmental impact, powder coating is usually the preferred choice for signage.

If you need colour matching flexibility, low-temperature processing, very thin coatings, or on-site or small-batch work, wet spraying can still be the right solution — provided its limitations are understood.

The correct choice depends on substrate material, component size, exposure conditions, aesthetic expectations, and regulatory requirements.

What is powder coating?

Powder coating is a dry finishing process. Finely ground powder (typically polyester, epoxy, or a hybrid) is electrostatically charged and sprayed onto a grounded metal component. The coated part is then cured in an oven, usually between 160–200°C, where the powder melts, flows, and chemically cross-links into a tough, uniform film.

Powder coating is the standard finish for aluminium sign profiles, trays, and posts in the UK signage industry because it offers an excellent balance of durability, appearance, and compliance.

What problems powder coating solves

Powder coating was developed to address many of the weaknesses of traditional liquid paints:

  • poor edge coverage

  • inconsistent film thickness

  • solvent emissions

  • limited outdoor durability

For external signage, these improvements are critical.

What is wet spraying?

Wet spraying (also called liquid painting) uses solvent-based or water-based paints applied with spray guns. The coating cures either through solvent evaporation, chemical reaction, or low-temperature baking, depending on the paint system used.

Wet spraying is widely used across manufacturing and fabrication, and it still has a place in signage — particularly for small runs, bespoke colours, touch-ups, and non-metal substrates.

Durability and outdoor performance

This is where the two systems differ most clearly.

Powder coating outdoors

Modern architectural powder coatings (typically polyester-based) are designed for long-term outdoor exposure. When applied and cured correctly, powder coating provides:

  • strong resistance to UV fading

  • excellent adhesion to aluminium and steel

  • good impact and scratch resistance

  • uniform coverage on flat surfaces and profiles

This is why powder coating is commonly specified for external trays, post systems, folded aluminium panels, and framing components.

Wet spraying outdoors

Wet-sprayed finishes can perform well outdoors, but performance is highly dependent on:

  • paint chemistry

  • surface preparation

  • film thickness

  • curing conditions

Lower-cost liquid paints may fade, chalk, or peel over time, particularly on south-facing signs or coastal sites. High-performance wet paint systems exist, but they often require tighter process control and higher ongoing maintenance.

Finish quality and appearance

Powder coating: consistency and robustness

Powder coating naturally produces a more even film build, which helps hide minor surface imperfections and provides consistent colour across large batches.

Common finishes include:

  • matt

  • satin

  • gloss

  • textured

  • fine metallics

Because powder coating is applied electrostatically, overspray is minimal and colour consistency between components is easier to maintain.

Wet spraying: flexibility and finesse

Wet spraying excels where colour accuracy or special effects are critical. It is often used when:

  • matching legacy colours or non-standard brand colours

  • applying very thin coatings

  • producing high-gloss automotive-style finishes

However, wet spraying is more sensitive to operator technique, environmental conditions, and drying time — which can lead to variation if not carefully controlled.

Substrates and compatibility

Aluminium components

Aluminium profiles and trays are particularly well suited to powder coating. Aluminium naturally forms an oxide layer, and when combined with proper pre-treatment (such as chromate-free conversion coatings), powder adhesion is excellent.

Wet spraying is possible on aluminium, but it relies more heavily on primer systems to ensure long-term adhesion.

Steel components

Steel can be powder coated or wet sprayed, but corrosion protection becomes more complex. Powder coating over properly pre-treated or galvanised steel provides good performance. Wet spraying on steel typically requires multi-layer systems (primer + topcoat) to prevent rust.

Environmental and REACH compliance

Powder coating and REACH

Powder coating is widely regarded as the more environmentally responsible technology:

  • no solvents

  • near-zero VOC emissions

  • minimal waste (overspray can often be reclaimed)

This makes powder coating inherently compatible with UK and EU REACH regulations, and it simplifies compliance for manufacturers and specifiers.

Wet spraying and REACH considerations

Wet spraying systems may contain solvents, pigments, or additives that fall under REACH controls. While compliant systems are available, they:

  • require careful material selection

  • often involve higher compliance documentation

  • may need additional extraction and environmental controls

Water-based paints reduce VOCs but can introduce drying and performance challenges.

Production efficiency and cost

Powder coating

Powder coating suits batch production and repeatable components:

  • fast application

  • consistent results

  • reduced rework

  • efficient use of materials

The main limitation is oven size and curing temperature, which can restrict very large or heat-sensitive components.

Wet spraying

Wet spraying offers flexibility:

  • suitable for very large items

  • works on heat-sensitive substrates

  • easier for one-off or repair work

However, it is typically slower, more labour-intensive, and more variable in finish quality.

Common mistakes and failure modes

Powder coating issues

Most powder coating failures trace back to poor preparation, not the powder itself:

  • inadequate cleaning or degreasing

  • poor pre-treatment on aluminium

  • incorrect curing temperature or time

  • sharp edges not radiused (leading to thin coating)

Wet spraying issues

Wet spraying failures are often more visible and progressive:

  • runs or sags from over-application

  • inconsistent colour or gloss

  • solvent entrapment

  • peeling or flaking due to poor adhesion

  • faster UV degradation

How to choose: practical guidance

Powder coating is usually the right choice when:

  • the sign will live outdoors long-term

  • aluminium profiles, trays, or posts are involved

  • durability and low maintenance matter

  • consistent appearance across multiple components is required

  • REACH compliance and environmental impact are important

Wet spraying may be suitable when:

  • matching a specific or legacy colour

  • working with heat-sensitive materials

  • producing one-off or small-batch items

  • carrying out repairs or on-site finishing

Final thoughts

For most modern signage applications, powder coating has become the default finish — not because wet spraying is obsolete, but because powder coating delivers predictable durability, regulatory simplicity, and consistent quality.

Wet spraying still has a role, particularly for specialist finishes and bespoke work, but it demands tighter process control and clearer expectations around maintenance and lifespan.

Understanding the strengths and limitations of each technology helps avoid premature failures, unnecessary rework, and disappointed customers — and ensures the finish performs as well as the sign itself.

Useful regulatory links

Below are reputable sources you can use for compliance checks, specifications, and best-practice guidance when specifying powder coating or wet spraying.