PLGN 4.03 Anti carbonation properties

Background

Anti carbonation refers to the ability of a coating to protect the substrate from attack by carbon dioxide. The presence of carbon dioxide and water in the substrate can lead to a mildly acidic solution which can attack concrete, masonry and metal reinforcing bars.

The coating prevents carbon dioxide coming into contact with the masonry substrate and hence the permeability of the coating to carbon dioxide is very important.

Carbon Dioxide Permeability

There is no national standard for measuring the gas permeability of a coating. There is however an industry accepted test in the UK and other parts of Europe. It is almost certain that this will form the European standard test for carbon dioxide permeability for inclusion under part 6 of a new European Standard for Masonry Paints which is being developed by CEN Standard Committee EN - 1062. CEN is the European standards committee equivalent to the UK British Standards Institute. (BSI) The results of this test are given in Sd values and it is very likely that the European committee will accept the UK industry standard of 50 units as a pass or fail criteria.
In other words, coatings with an Sd value of 50 or more are believed to act as barriers to carbon dioxide and would be termed as anti carbonation.

Carbon Dioxide Permeability of Weathershield Masonry Paints

Weathershield Trade Smooth, All Seasons and Textured Masonry paints have been tested using this method and the results show that the Sd values are 200, 130 and 2 units respectively. This means that Weathershield Smooth and All Seasons Masonry paints can be termed anti carbonation coatings against the above criteria but Weathershield Textured Masonry paint could not. This is entirely consistent because textured coatings are relatively porous due to the coarse extenders used to produce the textured effect.

Weathershield Policy on Anti Carbonation Claims

Weathershield Trade Smooth and All Seasons Masonry paint are promoted as having anti carbonation properties and the evidence noted previously will be used to substantiate these claims. This policy will be updated as the CEN standard is developed further.