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EXPLORING SURFACES
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EXPLORING SURFACES
ISO 12944 is the industry standard for the prevention of corrosion of steel structures using protective coatings. In order to meet this standard, a product has to undergo various laboratory tests. These tests depend, among other things, on the corrosivity class and durability range.
This page details the steps your product must go through to receive a particular ISO 12944 certification.
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Steel constructions are always subject to corrosion. They are exposed to a humid climate or are used underwater or underground. The ISO 12944 standard provides information on the coating technologies used, the criteria for the selection of coatings and requirements for the preparation of surfaces. This certification thus ensures maximum corrosion protection.
The ISO 12944 standard deals with the protection of steel structures using organic coatings that harden at room temperature. Coatings, such as powder coatings, that are hardened at a higher temperature fall outside the scope. For such coatings, it is better to use the Qualisteelcoat standard, which is very similar to ISO 12944. Qualicoat is the most suitable standard for aluminium.
The environment in which a product is used has an influence on its service life. In combination with the expected service life, the environment therefore determines the requirements of a coating system. The performance tests to be carried out are therefore geared to this.
ISO 12944-2 defines six corrosion classes:
| Class | Level | Area | Examples |
|---|---|---|---|
| C1 | Very low corrosivity | Heated buildings with a clean atmosphere, such as offices, shops, schools and hotels. | |
| C2 | Low corrosivity | Atmospheres with low levels of pollution: rural environments. | Unheated buildings where condensation may occur, such as warehouses and gyms. |
| C3 | Medium corrosivity | Urban and industrial environments with average sulphur dioxide pollution: coastal areas with low salinity. | Production areas with high humidity and some air pollution, such as in food production, in laundries and in breweries. |
| C4 | High corrosivity | Industrial areas with moderate salinity. | Chemical plants, swimming pools and shipyards. |
| C5 | Very high corrosivity | Industrial areas with high salinity. | Buildings with constant condensation and high pollution. |
| CX | Extreme corrosivity* | • Offshore areas with high salinity; • Industrial areas with extreme humidity and aggressive, subtropical or tropical atmosphere. | Industrial environment with extreme humidity and aggressive atmosphere. |
For structures used underwater or in the soil, ISO 12944 describes four environments in addition to the corrosion classes:
| Category | Environment | Examples of constructions and environments |
|---|---|---|
| IM1 | Fresh water | River installations and hydro plants. |
| IM2 | Sea or brackish water | Immersed structures without cathodic protection. |
| IM3 | Soil | Underground tanks, steel pipes and pillars. |
| IM4 | Sea or brackish water | Immersed structures with cathodic protection, such as offshore structures. |
The first part of the standard outlines a durability range. This is intended as a technical parameter that can help in preparing a maintenance plan. It is not a warranty period. That period is normally shorter than the durability range.
ISO 12944-1 defines the durability ranges as follows:
The first part of the standard outlines a durability range. This is intended as a technical parameter that can help in preparing a maintenance plan. It is not a warranty period. That period is normally shorter than the durability range.
| Laag (L) | Tot 7 jaar |
| Medium (M) | 7 tot 15 jaar |
| Hoog (H) | 15 tot 25 jaar |
| Zeer hoog (VH) | Meer dan 25 jaar |
To determine which tests need to be done to demonstrate your product’s compliance with the standard, it is first important to determine the corrosivity class, the intended environment and the durability range. For example, if it concerns a very high corrosivity environment (C5) and the durability range is also high (15 to 25 years), there are more laboratory tests and a longer test duration than for a C1 corrosivity class and a low durability range.
Tests for approval of coating systems are carried out on 150×75 mm panels. The panel thickness depends on the test, but is at least 3 mm. Unless otherwise agreed, the surfaces of the panels are blast cleaned to the minimum surface treatment class of Sa 2½ as defined in ISO 8501/1.
The surface roughness (profile) corresponds to ‘medium (G)’ as defined in ISO 8503-1. This can be checked by using a comparison tool as defined in ISO 8503-2. The panels are not bent. In all other respects, the panels correspond to ISO 7384.
Sometimes coated products as a whole are also subjected to the salt spray test and condensation test. This provides valuable information about weak spots in a coating system, such as welds, pinholes and sharp edges, but strictly speaking these tests are not covered by ISO 12944-6.
For application in standard atmospheric corrosion two test regimes are distinguished. Test regime 2 only applies to classes C4H, C5H and C5VH. The choice of regime 1 or 2 is free. Keep in mind that the current standard already indicates that regime 2 will probably become mandatory for these classes in the future.
Test regime 1
| Corrosion class | Durability range | ISO 6270-1 (water condensation) testing duration |
ISO 9227 (neutral salt spray test) testing duration |
|---|---|---|---|
| C2 | low | 48 hours | – |
| medium | 48 hours | – | |
| high | 120 hours | – | |
| very high | 240 hours | 480 hours | |
| C3 | low | 48 hours | 120 hours |
| medium | 120 hours | 240 hours | |
| high | 240 hours | 480 hours | |
| very high | 480 hours | 720 hours | |
| C4 | low | 120 hours | 240 hours |
| medium | 240 hours | 480 hours | |
| high | 480 hours | 720 hours | |
| very high | 720 hours | 1440 hours | |
| C5 | low | 240 hours | 480 hours |
| medium | 480 hours | 720 hours | |
| high | 720 hours | 1440 hours |
Test regime 2
| Corrosion class | Durability range | ISO 12944-6 Annex B (cyclical corrosion test) testing duration |
|---|---|---|
| C4 | very high | 1680 hours |
| C5 | high | 1680 hours |
| very high | 2688 hours |
| Corrosion class | Durablity range | ISO 2812-2 (water immersion) testing duration |
ISO 6270-1 (water condensation) testing duration |
ISO 9227 (neutral salt spray test) testing duration |
|---|---|---|---|---|
| IM1 | high | 3000 hours | 1440 hours | – |
| very high | 4000 hours | 2160 hours | – | |
| IM2 | high | 3000 hours | – | 1440 hours |
| very high | 4000 hours | – | 2160 hours | |
| IM3 | high | 3000 hours | – | 1440 hours |
| very high | 4000 hours | 2160 hours |
After carrying out the corrosion tests, the following should be assessed in accordance with ISO 4628:
ISO 12944-9 specifies the minimum requirements for protective coatings on offshore constructions and structures or structures related to them (such as those exposed to sea air or immersed in the sea or brackish water). Such structures are subject to extreme corrosivity (CX) and/or environmental class IM4.
ISO 12944-9 specifically distinguishes three corrosion categories each with its own testing regime.
| Corrosion class according to ISO 12944-9 | Cathodic disbonding ISO 15711 hours |
Sea water immersion ISO 2812-2 hours |
Cyclical corrosion test ISO 12944-9 annex B hours |
|---|---|---|---|
| CX (offshore) | 4200 | ||
| CX + IM 4 (splash zone) | 4200 | 4200 | 4200 |
| IM 4 (immersion) | 4200 | 4200 |
The prices of our laboratory tests are based on the tests required for the specific environment and the expected service life of the product. A product with a medium corrosivity (C3) requires fewer and shorter tests than a product with a high corrosivity and high durability range.
M2LAB uses the shortest possible lead times for laboratory tests for the ISO 12944 standard. In order to provide as much insight as possible into the status of different orders, we are currently developing a customer portal that provides an online overview of ongoing orders and current results.
In order to inspect your paint system, we need coated panels. The number of panels required depends on the desired corrosion class.
| ISO 12944-6 | Required number of panels |
|---|---|
| Test regime 1 | 12 panels 150 x 75 mm (3-5 mm thick) |
| Test regime 2 | 9 panels 150 x 75 mm (3-5 mm thick) |
| ISO 12944-9 | Required number of panels |
|---|---|
| CX (off shore) | 6 coated panels 150 x 75 mm (3-5 mm thick) |
| CX + IM4 (spash zones) | 12 panels 150 x 75 mm (3-5 mm thick) |
| IM4 (immersion) | 9 panels 150 x 75 mm (3-5 mm thick) |
Test results are strongly influenced by the quality of the pretreatment. Therefore, always make sure that this has been done very carefully. ISO 12944 specifies the methods suitable for this purpose.
Make sure that each panel has your own unique coding and provide a clear overview with all the necessary information of the coating system used on it. This contributes to clear and error-free reporting.
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