Peeling
Peeling paint is nearly always the result of poor surface preparation and in many cases is the result of poor surface preparation by the previous painter. New paint will not improve the adherence of the suspect old paint coating. Rather it is likely to make it slightly worse due to the stresses imparted as the new paint coating dries.

Waterborne paints take a few days to develop full adhesion especially if applied in heavy coats in dubious weather. This applies to many other paints as well.

Adhesion can be easily tested using the tape test. Note that the test result only applies to the spot where the test was done. An effort should be made to check how representative the result is of the entire job.

Tape test:
Carefully apply half of a clean 4cm strip of tape to a thoroughly cleaned test area previously cut in a cross pattern with a sharp razor blade. Ensure the tape is firmly adhered by pressing it down with your thumb nail. Hold the free ends of the tape at right angles to the test surface and yank it off with a sharp pulling movement away from the surface. Observe the removed tape for old paint and stain. If paint is easily pulled off, the adhesion of that coating must be considered suspect.

Peeling is an adhesion failure whereby the paint film peels away from the surface. There are two types of peeling:

• Total film failure back to bare surface (all coats are peeling);
• Intercoat failure (one or more coats separate from a lower coat).

There are several possible explanations for a paint job that fails due to peeling. The failure can be the result of inadequate surface preparation in not:

• Adequately sanding the old hard surface of an old paint to provide a good key for adhesion (Alternatively Resene Waterborne Smooth Surface Sealer may have been an option);
• Removing greasy contaminants from the substrate;
• Removing underlying loosely bound substrate contaminants such as wind blown dust and dirt or mould;
• Removing old paint degradation in the form of chalk;
• Removing substrate breakdown products such as:
• Weathered timber fibres;
• Old powdery weathered concrete;
• Efflorescence on concrete;
• Metal corrosion products.

Peeling can also be caused by applying the paint under conditions that hinder good film formation (very cold weather or very hot or windy weather that causes the paint to dry too quickly). The cause may be a combination of these factors. In situations involving many coats (more than 3-4) or old, solventborne paint, repainting can result in adhesion loss by the old paint and subsequent peeling. In cases where many layers of old oil-based paints are present, complete removal of the old and brittle layers of paint is recommended.