Technical reference

Coating Life-Cycle Cost: Method and Its Limits

Updated 2026-10

Key Facts

In AGA's published 30-year comparison the cheapest system on day one is the most expensive over life: epoxy/epoxy costs $2.94 per sq ft applied and $10.45 over 30 years, while IOZ/high-build epoxy costs about 10% more on day one ($3.23) and $3.62 per sq ft less over the same period ($6.83).
Day-one price separates the four paint systems by about $1.79 per sq ft; the 30-year column separates them by $3.79 and reorders them. Recoating cycles, not materials, decide the outcome.
Hot dip galvanizing's life-cycle figure equals its initial cost ($2.16 per sq ft) because the analysis assumes no maintenance over the period — which is the assumption doing the work, and the one to check against your own access and environment.
A 30-year horizon is a modelling choice, not a prediction. A longer one — AGA also publishes 75-year comparisons for bridges and infrastructure — shifts the result further toward maintenance-free systems; a structure with a shorter expected service life shifts it back.

Why applied price is the wrong comparison

Coating quotes arrive as dollars per square foot applied. That number is easy to compare and, on its own, systematically misleading: it prices the first application and nothing else. A system that is cheap to apply and needs recoating three times over the life of the structure can cost several times more than one that is dearer on day one.

The gap is not subtle. In the American Galvanizers Association's published comparison — a 250-ton project of typical size and shape in an industrial environment, 30-year analysis, 4% interest and 3% inflation:

System	Initial cost / sq ft	30-year life-cycle cost / sq ft
Epoxy / epoxy	$2.94	$10.45
IOZ / high-build epoxy (inorganic zinc primer)	$3.23	$6.83
Epoxy zinc / polyurethane	$3.59	$7.64
IOZ / epoxy / polyurethane	$4.73	$6.66
Hot dip galvanizing	$2.16	$2.16

Two readings follow, and the second is the useful one.

Day-one price barely separates the paint systems — $2.94 to $4.73 across four builds, a spread of $1.79. The life-cycle column reorders them: the cheapest paint system to apply (epoxy/epoxy at $2.94) is the most expensive to own at $10.45, while IOZ/high-build epoxy costs about 10% more up front and $3.62 per square foot less over the period. The system with the highest day-one price (IOZ/epoxy/polyurethane, $4.73) ends up the cheapest paint system to own, at $6.66.

What the calculation actually does

Life-cycle costing is not a forecast of prices. It is a structured comparison in which the same assumptions are applied to every candidate system:

Initial cost — surface preparation plus application, per square foot of coated surface.
A maintenance schedule per system — when spot repair, overcoat and full replacement fall, driven by the practical service life of each system in the specified environment. Practical service life is conventionally the point at which 5–10% of the coating has broken down and active rusting is present.
A design life over which the comparison runs — 30 years in this AGA analysis (AGA also publishes 75-year comparisons).
Discounting to present value, so future maintenance is not counted in tomorrow's dollars. Net present value is the usual method; average equivalent annual cost is the other common presentation.

Change any one of those and the ranking can move. That is the point of stating them.

Where these figures stop

The table above is a legitimate comparison, and it is also a specific one. Four limits are worth carrying with the numbers:

One environment. The comparison is for an industrial atmosphere. In C5 or immersion service the maintenance intervals shorten for every painted system, and in a benign C2 interior they lengthen.
One scale. A 250-ton project of typical size and shape, new steel. Small lots and field maintenance with access and containment price far above these figures.
A 30-year horizon. A modelling choice, not a prediction. A longer horizon — AGA also publishes 75-year comparisons for bridges and infrastructure — shifts the result further toward maintenance-free systems; for a structure with a shorter expected service life, fewer of the recoating cycles that create the gap ever occur and the advantage is correspondingly smaller.
Maintenance-free is an assumption, not a property. Galvanizing's $2.16 life-cycle figure is its initial cost because the analysis assumes no intervention over the period. That holds in the modelled environment; it is not a guarantee for any structure anywhere.

There is also a limit that is easy to cross without noticing. A life-cycle table shows which system costs less over a period under one set of assumptions — not how much damage a coating prevents, and not a payback period against the cost of corrosion. Published corrosion-cost totals generally include the money already spent on coatings and cathodic protection, so dividing one by the other produces a number that looks compelling and means very little.

Using it on a real project

The method transfers even when the published figures do not. Ask the contractor for the expected years to first maintenance in your environment, not just the applied price; decide the horizon from the structure's actual service life; and check whether recoating is even physically possible — on a structure that cannot be shut down or accessed, a maintenance-free system is worth more than any table can show.

For the systems and what they cost to apply, see protective coating cost, which also covers how the ISO 12944 corrosion category sets the system. For the weight-based pricing of galvanizing and the full AGA comparison in context, see hot dip galvanizing cost.

Source: American Galvanizers Association, Hot-Dip Galvanized Steel vs. Paint (2022) — 250-ton project, industrial environment, 30-year service life, 4% interest, 3% inflation; paint costs from KTA-Tator (2020), conventional spray, SP 6, eastern U.S.; the 75-year comparison in Costs Less, Lasts Longer uses 50,000 sq ft in a C3 industrial environment. Practical-service-life definition per KTA-Tator. Checked October 2026.