Wear and Corrosion of Metal Poles: Signs, Inspection, Repair or Replacement

Signs of wear in a pole

When the zinc wears away, corrosion moves on to the steel and thins the wall, and the load-bearing capacity falls with it (Corrosion protection). The most vulnerable zone is the base: moisture lingers there, de-icing salts get on the shaft, and the wind bending moment is greatest. Other causes are metal fatigue from wind and vehicle strikes. It is easiest to inspect from the bottom up:

What a white deposit and rust on a galvanised pole mean

A thin, even light grey film is the normal protective patina of zinc: it forms over time and slowly uses up some of the coating. A thick, loose white deposit points to prolonged wetting, standing water or salts; a brown tint means corrosion has reached the iron-zinc layer. Red-brown rust appears once the protection is used up, but foreign rust that rain has washed from ungalvanised parts looks the same. Measuring the zinc coating thickness and the wall thickness helps to tell them apart; typical defects are described in the article Hot-dip galvanising defects.

How often to inspect poles

There is no single interval for instrumental inspection that fits all poles: it is set by operating conditions and by the results of the previous inspection. For street lighting there are the Methodological Recommendations on the Maintenance of External Lighting Facilities in Settlements (order of the Ministry of Housing and Communal Services No. 253 of 21 August 2008), but they are recommendatory and cover routine maintenance. Poles that are inspected more often are those that:

• stand in an aggressive environment: near the sea, in an industrial zone, beside roads treated with de-icing salts;
• are tall or carry large luminaires, cameras, antennas or banners;
• stand where failure is dangerous: beside carriageways, in pedestrian areas;
• have been in service for a long time or have used up the design service life.

A regular check is made by the maintenance team; a detailed inspection with measurements is made by specialists when the check has shown signs of wear.

Unscheduled inspections are needed after a hurricane, an ice storm, a vehicle strike or a nearby fire. For galvanised structures, the article Hot-dip galvanising service life advises a check every year and after strong winds: this is a guide, not a regulatory requirement. The owner of the facility is responsible for meeting the inspection intervals and types (Inspection procedure and passportisation).

Which methods are used and how wear is assessed

The set of methods depends on the task and is agreed before work starts: the methods below are common practice, and the list for your facility is recorded in the work programme. The degree of section wear is determined from the actual cross-section area in the most damaged and most loaded places, disregarding layers of metal affected by corrosion (Diagnostics and assessment of technical condition).

The wall thickness is compared with the design thickness on the KM or KMD drawings, and the zinc thickness with the values for a new coating in DSTU EN ISO 1461:2024. How welds are checked during fabrication is described in the article Quality control of steel structures. Typical methods:

What the customer receives from an inspection

We agree the scope of work and the timing to suit your site. The customer receives a technical report on the condition of the structures and recommendations on repair, strengthening or further operation: the condition category (I–IV) and the degree of wear, and the results of verification calculations of load-bearing capacity that take into account the actual condition and refined steel properties. Where needed we carry out passportisation and prepare a strengthening design, and we can manufacture the structures required.

The technical methodology is set by DSTU 9273:2024, and the right to carry out an inspection belongs to certified specialists: Who may conduct a technical inspection. About the service in general: Technical inspection.

Repair or replace a pole: how the decision is made

The age of a pole is not in itself a reason to replace it, even if the design service life has been used up: it is a reason to inspect. First the cause is identified (corrosion, weld fatigue, impact, foundation settlement) and the scale: local damage is usually repaired, while widespread wear more often leads to replacement. Then a verification calculation is made with the actual wall thickness and weld condition: if, allowing for the wear, the pole carries the design loads, it stays in service; otherwise strengthening according to an engineered design or replacement is needed. We can design and manufacture a new pole (Lighting poles). Typical situations:

What the cost of inspection depends on

The cost is calculated individually; there is no universal price. It is affected by the number and height of the poles, access (work at height, an aerial work platform, switching off the power, excavation), the scope of the inspection (a visual check only, or also measurements, calculations and laboratory tests), the availability of drawings and passports, the consequence class, urgency and location, and for a strengthening design or a new pole, the type, height and complexity of the structure. More in the article Technical inspection cost.

For a cost estimate, send a list of the poles with height, type and year of installation, photos of the base and of areas with signs of wear, the location and the purpose of the inspection; if you do not know something, leave it blank and we will clarify.