Structural sections
SURFACE TREATMENT OF STEEL SECTIONS
WHAT IS CORROSION?
Corrosion is an undesired chemical decay of metals caused by air or water. The European climate is aggressive towards iron and steel constructions. It is therefore important to protect the metals and to consider these things when designing the constructions.
GENEREL INFORMATION ABOUT SURFACE TREATMENT OF STEEL SECTIONS
The term corrosion is defined as a general decay of a material when it reacts with the surroundings. Corrosion is a term primarily used in connection with metals.
The corrosion characteristics of materials depend – besides the combination, structure and treatment – to a high degree of the environment that the materials are exposed to. This is referred to as the corrosion environment.
The European climate is aggressive towards iron- and steel constructions. It is therefore necessary to protect the metals and to consider these things when designing the constructions.
CHOICE OF SURFACE
The choice of surface is extremely important to ensure the desired lifetime of steel sections. This is referred to as corrosion classes C1-C5 but when the lifetime of the steel is to be calculated/evaluated, one needs to know in which corrosion environment the material is about to be be placed. Only hereafter it is possible to advise a time limit.
The lifetime will change depending on the corrosion environment of the material. Omvendt kan man sige, at korrosionsklasserne spænder ret vidt og behovet for levetid kan variere.
To decide more accurately which surface treatment would be suitable for your project please read below and take contact to Triplan’s technical sector.
CHOISE OF CORROSION CLASSES
Triplan use only recognized European steel mills. We stock steel that meets demands from C1 to C5.
The summary shows the types of steel that Triplan use in the production.*
For steel sections that are installed on the outside of windproof plasterboards we use steel type AZ 185 that has been approved for corrosion class C4 or ZM 310 that is approved for corrosion class C5.
CORROSION CHARACTERISTICS
Triplan use only the very best materials but although the materials have been approved for C4 and C5, one must be aware that after treatment such as rollforming, punching of ventilation slots and cut edges, the corrosion resistance is reduced (contact Triplan’s technical department for clarifications on this). After treatment AZ 185 will typically be C3 and ZM 310 will be C4, however, ZM 310 can often be used in C5 environments. Materials such as AZ 185 and ZM 310 have a self-healing effect meaning that the exposed edges to a certain degree are protected by the galvanic element that is created when the plate is exposed to moisture.
Screws and bolts have a small surface compared to the surface of the steel. Triplan recommends using screws with the same surface (potential) as the steel profiles and their surface coating, preferably galvanized screws. If stainless screws are used, we recommend screws with an aluminum washer and rubber gasket to prevent galvanic corrosion
IMPORTANT
• AZ 185 cannot be used direct on alkaline plates
• Profiles with surface AZ 185 can be used in corrosion class C1-C3
• Profiles with surface ZM 310 and ZM 430 can be used in C1-C4 (C5 contact Triplan)
• Avoid all contact between steel and wet insulation materiales, wet concrete/cement-based slabs, wet timber, pressure-impregnated wood and other similar corrosive products
• Triplan-products must not be used in particularly aggresive environments without prior agreement with Triplan, be it eg. swimming pools, in high-salt air, in constant contact with water or in connection with chemicals, fumes, copper, lead, livestock manure, dust and ash or other similar corrosive environments See the link Swedish Technical Approval on our download page
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