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Pre-finished Steel Guarantees 101

11 January 2011 No Comment

There are many different pre-finished steel products available for the manufacture of roof cladding and wall cladding systems and all with what appear to be similar guarantees. Distinguishing which are genuine guarantees based on technical fact and which are being given because of commercial necessity can often be difficult.

How are guarantee periods determined for pre-finished steel?

Pre-finished steel guarantee periods are determined by a number of factors including:

  1. The products existing presence in-use in the market,
  2. The steel substrate metallic coating,
  3. The paint type and formulation,
  4. Physical testing.

It is the combination of each of these elements that enable the manufacturer to confidently give their products a guarantee period, for example Tata Steel’s Colorcoat HPS200 Ultra guarantee of 40 years.

What physical testing should pre-finished steel manufacturers undertake to back the guarantee period?

A suite of artificial tests and natural weathering exposures should be undertaken by the manufacturer to determine the performance of the pre-finished steel. Accelerated corrosion tests are undertaken in UKAS accredited laboratories to EN 13523 and consist of saltspray, prohesion, watersoak, humidity and Kesternich.

The extent of any edge creep, blistering, chalking and coating degradation is assessed. UV testing consists of a combination of artificial QUVA and QUVB, and natural weathering exposures, at sites throughout the world with different climatological conditions.  These tests assess the extent of colour fade and gloss retention of the pre-finished steel paint coating and are commonly given ratings of Ruv4 for colour performance and RC5 for corrosion resistance.

How does the steel substrate and paint coatings effect the guarantee period?

The synergistic effect of metallic coating type and weight, pre-treatment and corrosion resistant primer determine a pre-finished steel’s corrosion resistance at the cut edge and the period for which they are guaranteed. For example hot dip galvanising offers sacrificial protection at the cut edge, whereas Tata Steel Galvalloy (95% Zinc 5% Aluminium) offers both sacrificial and barrier protection thus slowing the rate of corrosion to the cut edge compared to traditional metallic coatings.

The topcoat paint formulation and thickness determine both the products aesthetics and durability. High performing paint systems such as Tata Steel Colorcoat HPS200 Ultra contain state of the art UV and heat stablisers plus other sustainable additives that ensure the paint maintains its colour and gloss for longer.

Why should I trust manufacturers in-house product testing?

The reliability of in-house tests and the resulting pre-finished steel guarantees should always be backed by independent testing. The integrity of these results should be independently verified by 3rd party accreditations such as the BBA, the French Corrosion Institute, Q-Lab Weathering Research and Atlas.

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