Introduction
One of the growing product segments in developing paint markets is the painting and re-painting of roofs. Almost every paint company in a rapidly developing paint market will have one or more roof coatings on their range whether it be a straight forward roof paint for metal or tile roofs a water proofing coating or a heat reflecting coating all these coating types have issues arising from problems in the field. The aim of this head scratcher is to show how an investigation of a complex roof paint problem can/should proceed:
Scene Setting
Up to about twenty years ago, most Southern African paint companies made premium quality roof coatings in oxide colors and did not have any major problems except when the applicators forgot to prepare the substrates properly or one them decided to make a very bright color that faded quickly.
If the substrate was oily or friable/powdery and applicator did not rectify these issues the paint would flake and peel. And bright colors under the high degree of sunshine present in Southern Africa will chalk and fade a lot quicker than a roof paint is expected to.
Then in the mid- to late-1990’s, we started to get oxide pigmented roof paints going lighter in six to nine months in Southern Africa, but not in all regions, and it wasn’t limited to one company’s paint but many companies’ paint, but only in certain regions.
On investigation, the lightening in color was found to be due to acid rain caused by industrial pollution/coal fired power stations and crop burning. For further details of the problem/solution, see Minimising the Effects of Acidic Airborne Pollution.
Once the acid rain issues were resolved, everything went quiet for about 10-12 years, but due to various economic/political factors, the roof paint market in Southern Africa changed from mostly oxide colors to various shades of medium to dark grey/charcoal and even black. We began to see early failures even on those formulations that were previously found to be acid rain inert. Also, it was not limited to one paint company or region. The only connecting factors were that they were roof paints and various greys. It wasn’t limited to color change—chalking also occurred. The situation got so bad for one paint company that they seriously considered totally dropping grey/charcoal roof paints from their range as although dark greys/charcoal accounted for 15% of their roof paint sales, they were 80% of their reported failures.After an in-depth Investigation, we found that the problem was multi-faceted. Certainly UV and IR play a big role in the problem, but you can only really reproduce the field problems in an accelerated manner by combining UV and IR in a cyclic test series. It also seems to be binder, pigment, film build and texture related. For more details, please see Mirmac APCC UV-IR Presentation Final.
The views, opinions and technical analyses presented here are those of the author or advertiser, and are not necessarily those of ULProspector.com or UL Solutions. The appearance of this content in the UL Prospector Knowledge Center does not constitute an endorsement by UL Solutions or its affiliates.
All content is subject to copyright and may not be reproduced without prior authorization from UL Solutions or the content author.
The content has been made available for informational and educational purposes only. While the editors of this site may verify the accuracy of its content from time to time, we assume no responsibility for errors made by the author, editorial staff or any other contributor.
UL Solutions does not make any representations or warranties with respect to the accuracy, applicability, fitness or completeness of the content. UL Solutions does not warrant the performance, effectiveness or applicability of sites listed or linked to in any content.
Hi Philip,
Your findings in your presentation were very interesting. We are always trying to accelerate outdoor aging in some way. Did you notice your combination of heating and UV to only work with the dark colors? I am curious to see if this would be a viable method for light colors. Thanks for your time!
Kind regards,
Jessica Luzier
Can I use car undercoat materials on my roof?
I really appreciate that you shared this amazing post with us, thanks for sharing and keep up the amazing work.
Thank you for reading!
Is prolonged exposure to oxidation one of the causes of discoloration of paint? Just like plastic
Carl No it is not the same as Oxidation in Plastics From what we have seen so far it is more related to a Heat/UV radiation promoted unzipping of the Polymer Back bone which then leads very quick Breakdown and Chalking /Failure
This blog is beneficial! Technological advances have created new approaches to the repainting of roofs. Thanks!
Thank you for sharing this amazing post with us. I really appreciate your taking the time to share this with us. Keep up the amazing work!
Very impressive, thanks a lot for sharing a helpful post with us.
I appreciate you sharing this blog article.Really thank you! Really Cool.