why 2K?

Architect's memo 61: December 1999

There is a chasm as deep and wide as the Grand Canyon existing in many architect's minds (and painters for that matter) between 'normal' paints and two-component (2K) protective coatings. There is a comfort bred of familiarity with the former, whilst the latter are simply alien and give thoughts as to why such mutants should even exist.

Apart from the semantic argument that decorative enamels are 2K, requiring oxygen from the air to convert them into useful coatings; the fact is that the most powerful coating chemistries are so reactive that they need to be kept apart until just prior to the coating operation. The question then becomes - just when are these more powerful chemistries needed?

There are three major parameters which would motivate one to use such a coating; the first of which is accessibility. If, through the nature of the design of a structure, parts of it will be difficult to maintain due to access considerations, it is wise to coat it at the very beginning with a superior coating system. For example, a grandstand may be built with the roof fixed to open steel beams. Whilst three sides of the beam are accessible for maintenance, the top is not without removing the roof. The paint system of this face (at installation) merits the highest consideration.

Intended life to first maintenance is the second major consideration. Durability of standard systems is generally well known from experience. Where this needs to be extended, possibly due to the high labour cost of maintenance, a higher performing system may be chosen. Steel window frames are an item that could fit into this category.

The third major consideration, and the most important, is the climate under which the coated system is expected to perform. Countries develop standards for paint performance, based on their climatic norms, and where these norms are exceeded, early failure will result. Although New Zealand's climate demands a high level of paint performance, there are many areas where standard paints will fall short.

For example:

• a standard anti-corrosive system will have been designed to operate with regular rain washings to keep it free from salt build-up
• a standard paving paint for a domestic garage will not withstand steel-wheeled trolleys in a factory environment
• a standard decorative paint will not withstand being tagged repeatedly with graffiti
• a standard acrylic will not prevent the degradation of cementitious substrates in an acidic environment

The list goes on. The key question to ask oneself - is this system/structure going to regularly experience conditions that would be outside the norm? If the answer is yes, then 2K may be the solution.

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