Corrosion Protection (ISO 12944)

Quick pick (TL;DR)

Find the ISO 12944 corrosivity category (C1 indoor → C5/CX coastal/offshore) and durability.
Hot-dip galvanizing for fasteners, gratings, small members and long maintenance-free life.
Paint (Zn-rich epoxy primer + epoxy + PU) for structures & large areas, with blast cleaning to Sa 2.5.
Duplex (galv + paint) for the harshest exposure.

Step 1 — Category & system

ISO 12944	Environment	Typical system (high durability)
C1–C2	Indoor / low	Epoxy ~80–120 µm
C3	Urban / industrial	~160 µm system
C4	High	~200 µm
C5 / CX	Coastal / offshore	~220+ µm or duplex

Step 2 — Paint vs galvanizing

Galvanizing: bolts, gratings, small members.
Paint: large structures, repairable.
Duplex: longest life in C5/CX.

Step 3 — Build the paint system

C5 coastal, high durability

Surface preparation abrasive blast to Sa 2.5 , profile 50–75 µm Coating build-up (DFT) primer : zinc-rich epoxy = 60 µm intermed: epoxy MIO = 100 µm topcoat : polyurethane (PU) = 60 µm total DFT = 220 µm Result → ISO 12944 C5, high durability (25 yr)

Zn primer (galvanic) + epoxy MIO (barrier) + PU (UV/colour). DFT + prep set durability.

Common mistakes

Under-spec corrosivity category.
Poor surface preparation.
Paint over galv without tie-coat.

Requisition & datasheet

Category, durability, prep, coats & DFT.
Galv thickness; colour; standard.

Frequently asked questions

What should I know about Corrosion Protection (ISO 12944)?

Find the ISO 12944 corrosivity category (C1 indoor → C5/CX coastal/offshore) and durability. Hot-dip galvanizing for fasteners, gratings, small members and long maintenance-free life. Paint (Zn-rich epoxy primer + epoxy + PU) for structures & large areas, with blast cleaning to Sa 2.5. Duplex (galv + paint) for the harshest exposure.

Which standards or codes apply?

ISO 12944 (paint, parts 1–9), ISO 8501 (surface prep / Sa grades), ISO 1461 (hot-dip galvanizing), NORSOK M-501 (offshore), SSPC/NACE.

Standards — ISO 12944; ISO 8501; ISO 1461; NORSOK M-501.