Painting defects
Pinholes
Solvents or air bubbles present in the substrate degas during the paint reticulation (especially using paints with high percentage of dry residue), causing small holes and defects. The problem can be solved by heating the items in the oven prior to painting, in which the air or solvents contained are removed.
Delamination (Peeling)
It is an important detachment of the paint that can occur as a result of advanced corrosion (after many years of materials aging) or due to incompatibility of the paint with the metal, for surfaces that are too smooth and unclean or for poor cross-linking or over-reticulation of the paint.
Mud cracking
Caused by excessive thicknesses, especially with high solid content water-based primers or paints. During reticulation, the coating fails to relax, creating defects and corrugations similar to dry mud.
Chalking
This is the phase shift of the pigments contained in some paints due to solar action; this can cause a serious chalking. Typical in epoxies and wall paints or if interior paints are used outside.
Cathodic detachment
These are oxidative defects that occur where there are important differences in electrical potential, commonly we speak of artifacts in intensive contact with electrolytic and saline solutions, such as: ships keels, underground pipelines, offshore platforms and building metal structures. Corrosion can be slowed down by using dedicated high salt (electrolytical) resistance paints and by employing cathodic control systems.
Bubbling
Defect found with liquid paint immediately after application or during reticulation. The bubbles cannot de-aerate and remain in the paint. The most common causes are: excessive paint agitation, intake of air during spraying, high viscosity, wrong formulation.
Spot corrosion (Pitting)
The formation of circular spot corrosions, usually small but which can cover the entire surface. This may be due to the aging of the paint or metal which, by creating small pores that act as an anode, give rise to external corrosion. Very common on ferrous materials exposed outdoors that have not been pre-painted with primer.
Blistering
Formation of circular bubbles, they occur as a result of corrosion or development of gases and transudations of salts and vapors. Humid environments, the presence of solvents and absent or ineffective pretreatment facilitate the formation of blistering.
Alligatoring
Large cracks in the coating intertwine to form a texture similar to the crocodile skin. It can occur as a result of surface expansion/shrinkage, too thin film, high working temperature or premature top coat application.
Flaking
It is a delamination with a fairly regular geometry, it can be caused by an unsuitable or difficult anchoring substrate (such as alloys and galvanized), by lack of primer or by thin and aged paint.
Cissing
Small holes caused by incompatibility with polluting elements present on the surfaces (such as grease, oil and silicone compounds) or due to imperfect or demixed formulations, which do not allow the paint to spread out optimally. The defect can also be found during the application of liquid paints, with the formation of deep holes (up to the metal), or after powder paints reticulation, with the creation of depressions and partial holes.
Wrinkling
Roughness defect that can appear, especially with solvent-based paints, in the case of too high thicknesses or if top coat is applied over other paint layers that are not completely dry. High application or environmental temperature can also favor this problem.
