Why the Cheapest Corrosion Protection Today Is Often the Most Expensive Over 20 Years — Think in Life-Cycle Cost (LCC)

TL;DR: The price that is "cheapest today" is rarely the "lowest total cost" for corrosion-protection work, because a cheaper system usually needs more repaint/replacement cycles, and each cycle carries hidden costs (re-access, surface prep, downtime) that can exceed the material cost. The correct way to compare is Life-Cycle Cost (LCC / TCO) per ISO 15686-5 — convert every future cost to today's value, then compare options on Equivalent Annual Cost (EAC). This article explains the method so you can see the mid- and long-term picture — the real numbers for your job must come from an on-site assessment, not from assumed defaults.

Corrosion-protection work — both protective paint systems (ISO 12944) and sacrificial anodes (cathodic protection) — is a hard call to make, because cheap and premium options look similar at installation. The difference shows up in years 5, 10, 20, when steel starts to corrode or coating begins to fail. This guide helps you see that difference before you decide.

1. Sticker price ≠ true cost

The price on a quote is only the initial cost. The true cost of a corrosion system accrues across the structure's whole life:

• Repaint / replacement every time the system reaches end of life
• Maintenance along the way
• Hidden costs of each work cycle (next section)

ISO 15686-5 (Life-Cycle Costing for constructed assets) sets the rule: keep every cost in today's money (real terms) and adjust future costs with a single discount rate — because ฿100,000 you must pay 10 years from now has a lower "present value" than ฿100,000 today.

Key point: comparing options of unequal life by sticker price alone is not fair — you must compare on Equivalent Annual Cost (EAC) = total life-cycle cost spread per year ("฿ per square metre per year" or "฿ per year").

2. The three costs the sticker price hides

(a) Number of repaint/replacement cycles — driven by the system's "expected service life," which ISO 12944 brackets by environment severity:

This is a planning range, not a warranty — a High-class system might repaint once in a 25-year horizon while a Low-class system repaints three times. That is the difference the sticker price does not tell you.

(b) Hidden cost per cycle — every time you return to redo the work, you pay not only for paint/anode material but for access (scaffolding / dry-docking), re-preparation of the surface, and — most expensively — downtime of the equipment or structure. On many jobs, downtime per cycle exceeds that cycle's material cost. A system that "removes a cycle" saves this whole block.

(c) The cost of doing nothing — see section 4.

3. Thinking in "cost per year" — an illustrative example

The numbers below are an illustrative example to demonstrate the method only — they are not market prices and not a quote for your job. Real numbers require an on-site assessment.

Suppose we compare two systems on the same area, over a 25-year analysis horizon:

The principle from the table: System A's low sticker price is offset by more repaint cycles plus higher hidden costs. Spread per year, System B is often cheaper — but not always. If the horizon is short (e.g. the structure only serves 7 years) or the environment is mild, System A may win. LCC is the tool that lets you see that break-even point instead of guessing.

4. "Doing nothing" has a cost too (but as a range, not a prediction)

Letting corrosion run has a real cost — the NACE/AMPP IMPACT (2016) study estimates the global cost of corrosion at ≈ 3.4% of GDP, and that best practice recovers roughly 15–35% of that damage.

But to be honest: the actual corrosion rate of steel is a range, not an exact figure — ISO 9223 classes severity as C3/C4/C5/CX (most of coastal/industrial Thailand is C4–C5), and ISO 9224 states explicitly that cumulative metal loss is non-linear (a power law). Multiplying "first-year rate × number of years" overstates loss by up to ~4× at 20 years.

So this article does not predict "how many years until your steel fails" or "how much you will save" — that requires a real survey. We give only the framework for understanding why the cost of delaying or neglecting protection tends to appear later and larger.

5. So what is the real cost for your job?

A trustworthy LCC figure for any job must come from real data:

• The real on-site environment (salinity/humidity/chemicals → C3–CX class)
• Surface area + existing condition
• The design life you need to protect
• For anode work: priced per drawing under DNV-RP-B401 (current demand + anode mass) — a per-project price, no off-the-shelf unit rate

Our engineering team can assess and compare options on a total-life-cost basis, with documentation suitable for quotes and government TOR review.

Sources

• ISO 15686-5 — Life-cycle costing for constructed assets (NPV / EAC framework)
• ISO 12944-1 — durability bands L/M/H/VH (a range, not a warranty)
• ISO 9223 / ISO 9224 — severity classes C1–CX + non-linear (power-law) metal loss
• DNV-RP-B401 — cathodic-protection (anode) design (priced per drawing)
• NACE/AMPP IMPACT (2016) — cost of corrosion ≈ 3.4% of GDP (macro anchor, not a per-customer figure)

The above synthesises definitions and principles of the cited standards with Thai application context — see the standards bodies' full texts via the links.

Frequently Asked Questions

What is Life-Cycle Cost (LCC) / TCO?

Total cost over the service life, not just the purchase price — including repaint/replacement, maintenance, and hidden costs, with future money discounted to present value (ISO 15686-5), then compared on cost per year (EAC).

Why can a pricier system be cheaper long term?

Because it needs fewer repaint/replacement cycles and removes several blocks of hidden cost (downtime/access) — adding up to a lower annual cost (depending on horizon and environment).

Does "15–25 years" per ISO 12944 mean a warranty?

No — it is a planning range (durability range), not a warranty. A warranty is a separate agreement in the contract.

Can a calculator just tell me "how many years my job pays back"?

The real number requires an on-site assessment (environment/area/drawing) — the principle shows the method, but a credible figure comes from a survey, not assumed defaults.

Can government / TOR work use LCC?

Yes, increasingly — compare on total life cost (not lowest price alone), state the study period, cite the standards, and attach certificates.

Request a life-cycle cost assessment / quote

Send your job details (environment · structure type · area/quantity · time horizon · standards required by the TOR) and our engineering team will assess the total life-cycle cost and compare your options:

• LINE OA: @406rrgvm
• Phone: 081-866-8368 (Khun Nawin)

Sahawatthanakit (1988) — corrosion protection, industrial coating systems, and sacrificial anodes for industrial, marine, and government work.