Flowcrete sheds some light on poor intercoat adhesion in resin flooring installations as part of its series on ‘industrial flooring problems’.
One of the primary reasons for the failure of industrial floors, poor intercoat adhesion occurs when a coating does not effectively adhere to the underlying layer. When the bond between the coatings is strong, the flooring system will maintain a functional surface for a longer period, acting as a barrier against contaminants, corrosives and impacts.
Different factors can contribute to an adhesion-related failure of a protective coating system. Poor intercoat adhesion can be identified by visible signs such as peeling, flaking or delamination of the top coating away from the previously applied primer or epoxy coating. Consequently, these problems expose the base coating or substrate to oils, greases, liquids and dirt at the site.
Top 4 reasons for poor intercoat adhesion
Improper preparation of the previous coating.
Proper preparation of the coating is necessary prior to applying multiple coats of the material. All contaminants including dust, dirt, water or amine blush must also be removed.
Most coatings have a range of time, or ‘recoat window’, within which a subsequent coat can be applied without additional preparation. Recoating outside of this window can lead to floor failure.
The recoat window time mentioned on the manufacturer’s product data sheet should not be exceeded; in the event it has been mistakenly exceeded, consult the manufacturer’s recommended recoat procedure.
When coatings are installed at temperatures lower than 5°F above the dew point, moisture may condense on the surface and act as a bond-breaker leading to intercoat adhesion problems.
Check the temperature and humidity of the substrate and air to ensure that the substrate’s temperature is at least 5°F above the dew point.
Not using a primer before applying the coating.
Ensure an appropriate primer is applied for the coating before starting the new layer.
Fixing a failure from poor intercoat adhesion
Sandblasting is an excellent solution for correcting poor intercoat adhesion. Alternatively, mechanical means such as grinding or sanding can be done to remove the surface contaminants and all of the flaking coating until the surface has a dull, unspoilt finish. The coating will need to be applied again, following the manufacturer’s application instructions to the letter.
In addition to being time- and labour-intensive, the rectification process is also very expensive. Therefore, the focus should be on prevention rather than repair by ensuring every precaution is taken to promote effective intercoat adhesion.
Image: Poor intercoat adhesion occurs when a coating does not effectively adhere to the underlying layer