Pinholes - Paint & Coating Defects
Paints and coatings are a combination of resins, solvents, additives and fillers that are formulated for a diverse range of conditions and applications and, as such, must be applied and cured correctly to suitably prepared substrates in order to ensure they perform to their maximum capability. Defects can manifest themselves at varying times in the lifespan of a paint or coating; the list below is not intended to be exhaustive and is indicative of the most common types of defects found.


Removal of a part or whole of the paint or coating film caused by impact by an object harder than itself.

Adhesion Failure

Where a paint or coating delaminates from the surface below, either within the differing coats of material or from the substrate.


Generally, two forms of blistering are noted: Osmotic – where the cause is associated with soluble salts, corrosion products, solvent entrapment and solvents from cargoes or processes; and Nonosmotic – which is associated with cathodic disbondment, cold wall effects and compressive stresses.

Bloom / Blush

Where the paint or coating film is exposed to condensation or moisture during curing.


Disintegration of the paint or coating binder when exposed to weathering or UV light; commonly seen within epoxies.


Surface contamination; usually moisture, oil, grease or silicones.


Generally, a stress-related failure due to movement, aging, absorption and desorption of moisture and a lack of flexibility within the paint or coating film.


Trapped air or solvent bubbles that have burst, leaving a crater effect as the paint or coating cures.


Low film thickness of paint or coating film, poor opacity of material or strong colour of the underlying coat.

Mud Cracking

Over application of heavily pigmented coatings such as inorganic zinc silicates.

Orange Peel

Failure of the paint or coating film to flow, commonly caused by poor application techniques or incorrect solvent blend.


Solvent or air entrapment within the paint or coating film.


Poor application techniques where the pressure used is too high.


Over-application and poor application techniques.

Rust Bloom / Rash

Where the paint or coating is of low film thickness and the surface profile has not been adequately covered.

Rust Spotting

Low film thickness not covering rogue peaks of the surface profile beneath; also seen from metallic contamination of a painted or coated surface by grinding dust, for example.

Rust Staining

Water run-off from a rusting surface above.


Over-application and poor application techniques.

Solvent Popping

Caused by incorrect solvent blends, porous surfaces, poor environmental conditions or too high a surface temperature.

The most common paint and coating defects originate not with the material itself, but with poor surface preparation and application techniques. This can be avoided by the use of a competent, experienced contractor. Contact us on 01274 721188 or email for all your surface preparation, painting and coating requirements.

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