BUYING GUIDES
Galvanizing and coating options for lighting poles
Steel lighting poles stand outdoors for decades, so corrosion protection matters as much as the structure. This guide explains the common options and what to state in your specification.
Updated
Hot-dip galvanizing
After cutting, forming and welding, the finished pole is dipped in molten zinc at around 450 °C. The zinc bonds metallurgically with the steel and covers the inside and outside, including welds and edges. Hot-dip galvanizing is the standard protection for road and high-mast poles.
Coating thickness standards
ISO 1461 sets the minimum mean coating thickness by steel thickness: 85 µm for steel thicker than 6 mm, 70 µm for steel over 3 mm up to 6 mm, and 55 µm for steel from 1.5 mm to 3 mm. ASTM A123 sets comparable minimums by product type and thickness. Actual coatings are often thicker. If your project needs more than the standard, specify it, as heavier coatings may need grit blasting before galvanizing.
Powder coating over zinc
A polyester powder coat over the galvanized surface, known as a duplex system, adds colour and extends service life, especially near the coast or in industrial air. The zinc must be cleaned and pre-treated before the powder is applied, or the coating can blister. Specify the RAL colour, gloss level and texture.
Choosing for the site
- Inland roads with low pollution: galvanizing alone is usually sufficient.
- Coastal, humid or industrial sites: specify a duplex system or a heavier zinc coating.
- Parks and city centres: a duplex system gives a uniform colour that matches street furniture.
- Where your engineer defines it, state the corrosivity category of the site, C1 to CX under ISO 9223.
Anchor bolts and fasteners
Galvanize at least the exposed part of the anchor bolts, and use hot-dip galvanized or stainless steel nuts and washers so the fixings do not corrode before the pole.
What to put in your specification
- Steel grade, for example Q235, Q355, S235 or S355.
- Galvanizing standard and any minimum thickness above it.
- Whether powder coating is required, with RAL colour and gloss.
- Site exposure or corrosivity category.
- Inspection: coating thickness readings, adhesion and visual checks.
- Touch-up method for damage during installation.
Inspection records
Ask for coating thickness readings taken with a magnetic gauge on each inspection lot, together with the visual inspection result. For our lighting poles, these records can be agreed with each order.
