Corrosion protection of steel structures according to ISO 12944

ISO 12944 is the international standard for corrosion protection of steel structures

This standard gives detailed instructions for the selection, design, application and maintenance of corrosion protection systems. The objective of ISO 12944 is to ensure the long-term protection of steel structures from corrosion and to reduce maintenance costs. The standard is relevant to industries such as shipbuilding, oil and gas, bridge-building, construction and other branches where steel structures are used.

Corrosivity categories and protection duration

ISO 12944 differentiates between six corrosivity categories for atmospheric environments (C1, C2, C3, C4, C5, CX) and four categories for structures in contact with water and soil (Im1, Im2, Im3, Im4). Im1 to Im4 as well as CX are covered by our partner Hempel.

In addition to the corrosivity categories the standard also distinguishes between four different protection durations*, i.e. the expected service life of a coating system until a first partial renewal is necessary:

  • Low (l) up to 7 years
  • Medium (m) from 7 to 15 years
  • Long (h) from 15 to 25 years
  • Very high (vh) more than 25 years

Corrosivity categories and examples for typical environments
(source ISO 12944-2:2018):

Contrary to the previous ISO 12944 standard (prior to 2018), the current version specifies dry film thickness (DFT) and minimum number of coatings (MNOC), which vary depending on the corrosivity category and coating type.

* The protection duration is not a warranty period, but a technical term and planning parameter that can help the owner to determine a maintenance programme («time to first maintenance»).

From C1 – C5: All-round protection with only a few products

Our product range speaks plainly:

  • We cover all systems from C1 to C5 h with only five products.
  • Thanks to its fine surface, Duopol EP micaceous iron oxide (MIO) paint
    is excellently suited as an intermediate coat under polyurethane and
    fluoropolymer top coats without the need for sanding at film thicknesses
    of 40 – 50 μm.
  • Since polyurethane systems change considerably in color and gloss after a protection period of > 25 years, we use our ultra-durable fluoropolymer line Vernidur FP for C5 vh, so that the object retains the same color and gloss
    even after such a long time.
  • The protection durations not listed in the table are also covered by our registrations: a protection duration «h» corresponds to «vh» in a lower corrosivity category (e.g. C3 h = C2 vh, C4 h = C3 vh, C5 h = C4 vh, C5 l = C4 h = C3 vh, etc.):

Systems tested according to ISO 12944-6:

Request more information directly on our competence page. Below you can view the flyer in PDF format.

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