Documentation

The mechanical action of rubbing, scraping, scratching, gouging, or erosion.

Probable Causes:
Removal of a portion of the surface of the coating or, in severe cases, removal to expose the substrate by contact with another object, such as the use of metal chains for lifting, cargo, fenders, or the grounding of a surface.

Prevention:
Use of abrasion resistant coatings formulated with particular regard to resins and extender pigments. With Severe cases of abrasion, the effects will be reduced or limited only by an abrasion resistant coating.

Membrane fails to adhere to substrate or underlying coats of coating.

Probable Causes:
Surface contamination or condensation, incompatibility between coating systems, or exceeding the overcoating time.

Prevention:
Ensure that the surface is clean, dry, and free from any contamination and that the surface has been suitably prepared. Use the correct coating specification and follow the advised overcoating times.

Very large (macro) crazing/cracking that resembles the skin of an alligator or crocodile. Cracks may penetrate through to the undercoat or down to the substrate.

Probable Causes:
Internal stresses in the coating where the surface shrinks faster than the body of the coating film. Excessive Film thickness and limited coating flexibility. Application of a hard topcoat over a more flexible soft undercoat. Application of topcoat before the undercoat has dried.

Prevention:
Use correct coating specification and compatible materials. Avoid excessive film thickness. Avoid application at high ambient temperatures.

Staining of a coating film by diffusion of a soluble coloured substance from the underlying coating to give undesirable discoloration or staining. Often seen where bituminous or tar-based products are overcoated with topcoats in which the tar or bitumen is soluble. Also occurs with emulsion paints.

Probable Causes:
Bleed through is generally a full or partial redissolving of the previous coat or an ingredient of a previous coat and can occur when strong solvents are used in the topcoats.

Prevention:
Use correct coating specification and materials. Use compatible materials. Use an appropriate sealer coat if possible.

Dome shaped projections or blisters in the dry coating film through local loss of adhesion and lifting of the film from the underlying surface. Blisters may contain liquid, vapor, gas, or crystals.

Probable Causes:
Many mechanisms can be involved, including osmotic gradients associated with soluble salts, soluble pigments, corrosion products, retained solvents, and solvents from cargoes. Nonosmotic blistering is associated with cathodic disbonding, thermal gradients related to cold wall effects, and compressive stress.

Prevention:
Ensure correct surface preparation and application. Apply a suitable coating system after testing for soluble salts. Consider the possibility of the different blister mechanisms in the particular environment.

A hazy deposit on the surface of the coating film resembles the bloom on a grape, resulting in a loss of gloss and a dulling of colour.

Probable Causes:
Coating film exposed to condensation or moisture during curing, especially at low temperature (common phenomenon with amine cured epoxies). Incorrect solvent blend can also contribute to blooming.

Prevention:
Apply and cure coating systems under correct environmental conditions and follow the manufacturer’s recommendations.

Bubbles within a coating film appear as small blisters. These may be intact or broken (leaving a crater). Can Be found in excessively thick coating films, especially if spray applied, and also with roller application. This Should not be confused with blistering.

Probable Causes:
Trapped air/solvent within the coating that is not released before the surface dries. Air entrainment during mixing. High ambient temperature during application. Also seen when overcoating antifouling without removal of the leached layer and zinc silicates. Can be found with factory applied coatings where application is by dipping, electrodeposition, or roller coating.

Prevention:
In spray application, adjust viscosity with thinners and follow data sheet requirements for maximum application temperature. Use correct mixing equipment to ensure air is not stirred in during mixing. Apply a mist coat. Add a defoaming agent to emulsion paints.

A friable, powdery layer on the surface of a coating film. A change of colour or fading is also seen. Chalking Rates vary with pigment concentration and choice of binder. Chalking is a known characteristic of certain coatings, for example, epoxy coatings.

Probable Causes:
Disintegration of the coating binder on exposure to weathering and/or ultraviolet light.

Prevention:
Apply a suitable topcoat with high resistance to chalking and with ultraviolet resistance.

Fine cracks that do not penetrate the topcoat of a coating system. Some checking can be so minute that it’s impossible to see without magnification.

Probable Causes:
Typically, a formulation and/or a specification problem. As with cracking, stresses are developed that cause the surface of the coating film to become brittle and crack. Limited coating flexibility.

Prevention:
Use a correctly formulated coating system.

The splitting of a dry coating film through at least one coat to form visible cracks, which may penetrate down to the substrate. Cracking comes in several forms, from minute cracking to severe cracking.

Probable Causes:
Cracking is generally a stress related failure and can be attributed to surface movement, ageing, absorption and desorption of moisture, and general lack of flexibility of the coating. The thicker the coating film, the greater the possibility it will crack.

Prevention:
Use correct coating systems, application techniques, and dry film thicknesses. Alternatively, use a more flexible coating system.

The formation of small bowl-shaped depressions in the coating film. Not to be confused with cissing.

Probable Causes:
Trapped air or solvent bubbles that have burst, leaving small craters as the coating dries. The coating has insufficient time to flow into a uniform film.

Prevention:
Improve spray technique, apply a mist coat, and avoid air entrainment during mixing. Add thinners as recommended by the coating supplier.

Similar to checking but the cracks are generally wider and penetrate deeper into the film.

Probable Causes:
Application temperature too low, incompatibility with previous coating, aging, or high film thickness.

Prevention:
Apply a thinner coat of membrane, add slower drying solvent, check that application and drying conditions are correct for the coating system used, and check compatibility.

The development of small wrinkles in the polyurethane coating film in a pattern resembling a crow’s foot.

Probable Causes:
Usually due to the surface drying rapidly to form a skin, which then wrinkles as solvent slowly evaporates from the soft underlying coating.

Prevention:
Apply a thinner coat of polyurethane membrane, add slower drying solvent, and check that application and drying conditions are correct for the membrane system used.

A form of adhesion failure where membranes flake from the substrate. A familiar sight on wood substrates and on galvanising.

Probable Causes:
Incorrect membrane primer system used. Either no or an incorrect pretreatment used for certain substrates, for example, non ferrous or galvanised. Also, poor application techniques. May also be attributed to differential expansion and contraction of membrane and substrate, for example, wood. Can be the result of ageing of the membrane system.

Prevention:
Use the correct coating system and pretreatment primers/sealers.

Discoloration, detachment and/or blistering, and general degradation of a membrane film.

Probable Causes:
Effect of high temperature is often applied to the reverse side of a steel plate from burning, welding, or fire.

Prevention:
Ensure that all welding/burning is completed prior to priming and membrane coating.

Cracks that radiate from a point of impact.

Probable Causes:
Impact damage to a relatively brittle coating. Often seen on glass fibre reinforced plastics. Also occurs when steel is deformed by impact.

Prevention:
Prevent impact damage.

Cracks that radiate from a point of impact.

Probable Causes:
The contamination could be present due to inadequate washing down, salts from weathering of shop primer,or deposits from nearby operations.

Prevention:
Carefully inspect and test the surface before coating application and wash down with fresh water if required.

The dried coating film has the appearance of a dried-out mud flat. The cracks appear as a network that can vary in size and amount.

Probable Causes:
Generally, overapplication of heavily pigmented primers such as inorganic zinc silicates or water-based coatings, although can occur with other over-thick systems like PU membranes.

Prevention:
Apply only the recommended coating thickness. Use recommended application techniques with suitably formulated products.

A uniform, pock marked appearance, in particular of a spray applied coating, in which the surface of the coating film resembles the skin of an orange.

Probable Causes:
Failure of the coating film to flow out. Usually caused by poor application techniques, incorrect solvent blend, or too high thixotropy.

Prevention:
Use correct application techniques with suitably formulated products.

Similar to flaking, although peeling tends to be associated with soft and pliable fresh coatings that can be pulled away from or spontaneously flake away from the substrate or from between coats, due to loss of adhesion.

Probable Causes:
Peeling is the reduction in bond strength of the coating film due to contamination or incompatibility of coats.

Prevention:
Use the correct coating system and specification applied to clean and uncontaminated surfaces.

The formation of minute holes in the wet coating film during application and drying, due to air or gas bubbles that burst, giving rise to small craters or holes that fail to coalesce before the film has set.

Probable Causes:
Solvent or air entrapment within a coating film. A common problem when coating porous substrates such as zinc filled primers, zinc silicates, and metal sprayed coatings. Pinholes can also be caused by incorrect spray application or incorrect solvent blend.

Prevention:
Use correct application techniques with suitably formulated products. Correct solvent blends and environmental conditions. Check spray equipment and distance of spray gun from the surface. Apply a mist coat.

A rippled effect on the surface of the coating.

Probable Causes:
Strong wind blowing across the surface of the wet coating causes it to ripple. Where this occurs on the underside,the ripples can hang down in the form of small stalactites. Can also be caused by poor application techniques.

Prevention:
Do not apply coating under unfavourable conditions. Use correct application equipment and workmanship.

A narrow downward movement of a coat of membrane, often apparent from accumulation of excessive quantities of coating at irregularities such as cracks and holes where the coating continues to flow after the surrounding surface has set.

Probable Causes:
Overapplication of coating, excessive use of thinners, incorrect (or lack of) curing agent, or poor workmanship.

Prevention:
Use correct application techniques and apply at the recommended dry film thickness.

Fine spots of rust that appear on a coating film, often a thin primer coat. The initial spots rapidly spread over the surface, resulting in a film of rust through which the individual spots are difficult to discern.

Probable Causes:
Low film thickness, often in combination with a high surface profile.

Prevention:
Ensure that an adequate thickness of a primer coat is applied to cover the surface profile, and check that the surface profile is not too large.

A light staining on the surface of the coating caused by the precipitation of ferrous oxide from adjacent exposed steel.

Probable Causes:
Water runoff from a rusty surface above a soundly coated surface. Rust staining occurs when the rust is wetted out and contaminated water runs over and discolours other items or locations. Usually more of an eyesore than a defect. The coating itself may not be defective, only stained.

Prevention:
Ensure adequate design and suitable maintenance.

Loss of adhesion between coats of membrane.

Probable Causes:
Provided that compatible membrane materials have been used, delamination defects are generally related to poor surface preparation and application defects, such as contamination between coats, exceeding overcoat times, or application to a glossy surface.

Prevention:
Ensure that no contamination occurs between membrane coats. Follow the recommended overcoating intervals.Lightly abrade and clean glossy surfaces between coats.

Sags are caused by the downward movement of a coat of membrane that appears soon after application and before setting, resulting in an uneven area with a thick lower edge. They are usually apparent on local areas of a vertical surface and, in severe situations, may be described as curtains.

Probable Causes:
Overapplication of coating, excessive use of thinners, incorrect (or lack of) curing agent, or
poor workmanship. Could, in extreme circumstances, be a formulation problem.

Prevention:
Use correct application techniques with suitably formulated products.

The sedimentation of the solid constituents comprising pigments and extenders from the binder and solvent while standing in a container. Settlement that occurs after mixing and during application can result in indifferent shades and performance in different areas.

Probable Causes:
Old stock, heavily pigmented coating, and incorrect formulation of product. Can be a problem with zinc rich primers.

Prevention:
Use products within shelf life. Use adequate mixing procedures. Keep coating mixed or recirculated during spray application.

Formation of a layer of skin on the paint surface in a container.

Probable Causes:
Absence of Anti skinning agent, use of non airtight container, hot storage conditions. Often occurs in partly used cans.

Prevention:
Use an airtight container, and store according to the data sheet.

Eruption of the surface of the coating film. Wrinkling and blistering, which lead to a weak surface and ultimate coating breakdown.

Probable Causes:
Incompatible coating systems used. Topcoats with a strong solvent blend can react with previous and weaker solvent blended coatings. Overcoating before the previous coat has adequately hardened.

Prevention:
Use correct coating specification, overcoating times, and materials. Conduct compatibility trials withundercoat/topcoats.

Discoloration or gradual decrease in colour of membrane when exposed to sunlight/weather. May be accompanied by loss of gloss. In some situations, it may resemble chalking but without the powdery surface.Fading tends to accelerate in the presence of moisture.

Probable Causes:
Incorrect pigmentation, use of non-light stable organic pigments, atmospheric contamination, porous substrate.

Prevention:
Use correct coating systems that resist ultraviolet light and fading. Use a coating with light stable pigments.

The development of wrinkles in the coating film during drying.

Probable Causes:
Usually due to the initial formation of a surface skin with solvent based coating. Can arise from overcoating before the previous coat has adequately hardened. Over thickness, particularly with alkyd coatings.

Prevention:
Use correct coating specification and materials, and ensure adequate mixing, application, and curing by following the product supplier’s recommendations.