Which finish lasts longest outdoors?

For outdoor enclosures, a polyester powder coat over zinc pre-treatment is the usual baseline, with stainless steel (304/316L) or aluminium with anodizing for corrosive or coastal sites. In harsh, salt-spray or washdown environments, 316L stainless with a passivated or powder-coated finish outlasts coated carbon steel. Longevity is environment-specific, not a single winner.

Is anodizing only for aluminium?

Yes. Anodizing grows an oxide layer on aluminium; it does not apply to steel. For steel the equivalents are zinc plating, galvanizing or powder coating. If you need a hard, thin, wear-resistant surface on aluminium, anodizing (type II or hard type III) is the right call; for colour and corrosion resistance on steel, powder coat.

How thick is a powder coat?

A typical polyester powder coat is 60-120 microns per face (about 40-80 microns for thin films, up to 120+ for heavy-duty outdoor). The thickness affects both corrosion resistance and fit, so bores and threads are masked or tolerance is set on the bare metal. Specifying the film thickness (for example 80-120 microns) removes ambiguity.

Powder coat vs plating vs anodizing: which costs more?

Roughly, zinc plating is cheapest, powder coating mid-range, anodizing similar to powder coat for aluminium, and hot-dip galvanizing cost-effective for thick steel. The real cost driver is preparation and the coating thickness the environment demands, not the process name. We quote the finish against the IP rating and life you need.

Can I powder coat over galvanized steel?

Yes, with the right pre-treatment. Powder coating over galvanized (or zinc-plated) steel is common for outdoor enclosures because you get both cathodic protection and a thick top coat. The key is surface preparation so the powder adheres and the zinc does not outgas during curing. We specify the pre-treatment at quotation so the finish holds.

Does the finish affect IP rating?

Indirectly. The finish protects the substrate from corrosion that would otherwise let water into seams, but the IP rating comes from the gasket and assembly, not the paint. A perfect powder coat on a box with a poor gasket is still not IP66. Specify both: the rating from the seal, the finish from the environment.

Powder Coating vs Anodizing vs Plating for Metal Enclosures

Powder coat is the default outdoor finish for steel; anodizing is aluminium-only and hard; plating and galvanizing are the cheap corrosion base. The right choice pairs the substrate with the environment and the IP rating — and none of them replaces a good gasket.

Powder coat

60-120 microns, thick top coat, colour + corrosion resistance. The default for outdoor steel enclosures.

Anodizing

Aluminium only. Thin, hard, wear-resistant oxide. Good for coastal aluminium parts.

Plating / zinc

Cheapest corrosion barrier; hot-dip galvanize for thick steel. Often a base under paint.

Reference

Finish, material and environment together

No finish wins on its own. The right choice pairs the substrate with the environment and the IP rating. This table is the starting point we use at quotation.

Environment	Good combination	Why
Indoor, dry	CRS + powder coat	Cheap, presentable, enough protection
Outdoor, normal	CRS + zinc pre-treat + powder coat	Cathodic base plus thick top coat
Coastal / salt	316L stainless, passivated or coated	Stainless resists chloride; coating adds life
Washdown / hygiene	304/316L, smooth weld, passivated	No coating to chip; easy to clean
Aluminium part	Anodized (type II/III)	Hard, thin, corrosion-resistant

Coating thickness is specified in microns. Bores and threads are masked or tolerance is set on bare metal so the finish does not close them.

Cost

What actually drives the price

The process name is not the cost — preparation and the film thickness the environment demands are. Zinc plating is cheap; a heavy-duty 120-micron outdoor powder coat costs more but avoids repainting. We quote the finish against the life you need rather than padding a generic 'powder coat' line.

Standards & compliance

Fit

The finish and the seal are separate

A perfect coat on a poor gasket is still not IP66. Specifying finish and IP rating as one package avoids the classic mismatch where the paint is fine but water enters at the door. We confirm both from the environment you give us.

IP rating comes from gasket + assembly
Finish comes from the environment
Mask bores/threads or tolerance bare metal
State film thickness in microns

FAQ

Surface finish questions

{''.join( '

%s

' % (q, a) for q, a in A4_FAQ)}

Tell us the site, we spec the finish

Coastal, washdown, indoor or outdoor — give us the environment and the IP rating, and we return the substrate, finish and film thickness as one quotation.

Get a quotation