Paint Failure On Metal Surfaces: Causes & Solutions
Sprayed paint coatings are used on a wide variety of decorative and functional architectural metal components in numerous locations ranging from corporate offices to high street superstores. However for a number of reasons the paint used on these metals can fail, creating a hideous aesthetic appearance and potential performance problems. There are numerous reasons why paint failure on metal surfaces can occur; this blog identifies a number of these before providing a solution.
This is where a paint coating bubbles up in blisters, this means that the paint is no longer in some places directly attached to the metal substrate underneath. This issue can arise when solvent based paints are sprayed onto a surface which is too warm due to high temperatures known as solvent boil). But more likely causes include applying too thick a coating of paint onto the surface and applying a second coat of paint before the first coat has fully dried. This is because the solvent becomes trapped and expands creating the blistering effect. Blistering can also occur overtime if the paint film is porous, (allowing moisture to penetrate the paint film) this is common in extremely warm, high humidity environments.
One form of paint failure occurs it can result in a coat of paint splitting. The subsequent aesthetic effect produced is cracks and flakes on the paints surface, the most severe examples are often referred to as ‘crocodiling’. Cracking can be spotted early on in the form of hairline cracks which occur in the paints surface before chunks begin to fall off. The cause of this problem is using poor quality paints which are not compatible with the finish they are applied over. The situation is made worse by inadequate preparation resulting in limited adhesion between coats. Another issue may be that the cracked paint lacks flexibility or has poor adhesive qualities.
In the case of adhesion failure, paint loses its adhesion to the metal surface (substrate) beneath. The primary causes of adhesion failure are poor preparation or unsuitable paint systems. No paint system will adhere to the metal substrate for very long if it hasn’t been properly cleaned and abraded. Where metal structures are subject to weather exposure, metals need careful preparation followed suitable primer and topcoat systems, according to intended use and environment.
Over time a painted surface can become stained with dirty patches. This is a result of dirt, dust and general detritus mater becoming embedded in the paint film. Air-borne pollution and general dirt are more likely to be attracted to a surface which has a rough finish, or are not naturally washed by rain. Contaminants can be corrosive and in some cases penetrate the coating. This is why regular cleaning is often a requirement where coated items such as cladding or window frames etc. carry a warranty.
Over a period of time the film of paint can begin to erode. This process causes the paint to decompose into a chalky layer and often change colour or appear ‘bleached’. The problem is less noticeable on white or very light pastel shades but may still be there and can be easily demonstrated by simply wiping a hand over the surface. If it has chalked, it will leave a white residue on the hand. The process is usually caused by exposure to UV (ultra-violate light) and atmospheric pollutants. Some paint formulations (such as epoxies) have little resistance to UV and some pigments and binders have similar issues. However there are architectural quality paints which are particularly good at resisting UV and therefore chalking. Most modern cars have a clearcoat / lacquer over the colour which is not only hard wearing but reflects UV thus preventing chalking and colour changes.
The best insurance against the re-occurrence of paint failure is to use a Company that understands surface coating ‘Chemistry’ and ‘Technology’. This means that a full appreciation and appraisal of the surface material, condition and requirements are properly analysed. Once this is understood, the correct coating specification can be designed and implemented. Our knowledge of surface preparation and materials Chemistry means that you will receive the correct and thorough preparation, materials selection, and application.
ORS carries-out highly professional spray painting to a variety of surfaces for a wide range of clients. Our knowledge, experience, and expertise allow us to provide the best, long lasting results and avoid paint failure altogether. Appointing the services of ORS ensures that your project receives an aesthetically beautiful, yet durable finished product.