Long Term Corrosion Protection

Where steelwork needs to be protected from a corrosive coastal atmosphere, obviously heavy-duty galvanic corrosion protection is required. This can be achieved by a number of methods; according to the Australian Standard AS/NZS 2312, “Guide to the protection of structural steel against atmospheric corrosion by the use of protective coatings”, superior galvanic corrosion protection is offered by the use of inorganic zinc silicates or zinc rich epoxy coatings in high corrosivity areas.

Dulux Aquagalv is a waterborne inorganic zinc silicate coating that complies with
AS/NZS 2312 for long term corrosion protection and thus compares very favourably with other forms of galvanic corrosion protection such as hot dip galvanising. And at less than 10g of VOC per litre, it is also a low environmental impact option.

Having said that, our other zinc-rich primers are cost-effective alternatives. Whilst they do contain higher levels of VOCs than Aquagalv, they have other advantages for the eco savvy specifier. The Zincanode range offers excellent galvanic corrosion protection, has virtually no HAP emissions, require no chemical pre treatments, are chromate and lead free, and can be applied and cured at room temperature, which make them very appropriate choices as well.

Dry, sheltered and inland areas present a very low corrosivity environment, and therefore exposed steelwork requires lower film builds and/or fewer coats than in areas closer to the coast.

Whilst concrete structures have been designed in an attempt to avoid the need for protecting steel against corrosion, a concrete structure contains almost as much steel as an equivalent-sized steel structure. Furthermore, the embedded steel is only protected against corrosion by the surrounding concrete as long as the concrete remains highly alkaline, and protected from salts. In our coastal developments, exposed to the increasing acidity of rain and atmospheric pollution, the concrete readily neutralises, and allows the concrete reinforcement to corrode and expand in volume, forcing cracks and deterioration of the concrete. This common phenomenon is called spalling.

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Fact 3

The lightweight steel and concrete structure was designed to permit dismantling for possible re-design and/or recovery of all components. Long-term durable zinc-rich primers and acrylic topcoats protect the steelwork.

Dulux Head Office