MARINELINE® & CHEMLINE® COATINGS FOR INDUSTRY

APC Troubleshooting Coatings Failure #1

Coating Failures - Causes and Remedies

Recognizing the type of coating failure encountered in the field along with understanding its cause and how to rememdy it can lead to early correction and/or major reductions in maintenance costs while maintaining the overall appearance. All coatings eventually fail by weathering, especially exterior weathering. However, premature failure is a costly problem that oocurs all too frequently. This document addresses its probable cause, and then gives methods of remedy.

Description Causes Remedy
ABRASION DAMAGE. Mechanical damage. Physical damage by abrasion (also impact). Provide fendering protection; spot repair and use more abrasion or impact-resistant coatings.
  APPLICATION MARKS. Poor quality tools. Temperature too hot causing paint to cure too quickly and not allowing the product to flow naturally. Abrade back to flat even surface and refinish, considering applications and temperature conditions.
BLISTERING. Small to large broken or unbroken bubbles; surface may feel like sandpaper to touch. Surface contamination prior to paint application. Solvent entrapment due to paint being applied too thickly or overcoated too soon. Moisture entrapment during coating. Coating applied when humidity was too high. Blowers in enclosed areas to accelerate solvent release; adequate cleaning of surface contamination; proper levels of cathodic protection; abrade back all blisters, fill where necessary and recoat.
BLUSHING. Flat finish with milky appearance. Moisture condensation in high humidity with fast evaporating or unbalanced thinner in spray application. Abrade back until blushing is cleared and recoat considering the relative humidity and temperature; respray with retarder add to thinner.
  CHALKING. Poor gloss, powdery surface. Prolonged exposure to Ultra Violet rays. Poorly mixed paint. For a permanent cure, abrade back and recoat ensuring the paint is properly mixed.
CHECKING. Narrow breaks, usually short, in topcoat that exposes undercoat. Limited coating flexibility; too thick a coat; or applied at too high a temperature. Sand or mechanically remove checked coat and apply another coat.  
COATING APPLIED TO DAMP SURFACE. Heavy wrinkling. Moisture on substrate distorts wet film. Remove by scraping or sanding and recoat under dry conditions.  
CRACKING. Deep cracks in coating that exposes substrate. Coating shrinkage; limited flexibility; excessive thickness; or applied/cured at too high a tempature. Sand, blast, or mechanically remove total coating and appliy new coat.  
CRATERING. Also called pitting. Small, uniform indentations in film. Air pockets trapped in wet film during spraying. Sand or blast to smooth finish and apply additional coats.  
  CRAZING. Appearance of shattered glass. Extreme temperature changes during coating. Incompatible overcoating. Coating applied too thickly or overcoated too soon. Abrading back and repainting may curing the problem, however, it is more likely that the complete coating needs to be removed and an appropriate coating re-applied in accordance with recommended specification.  
DELAMINATION. Peeling from undercoat or substrate. Separation/lifting of paint from chalky substrate or smooth, poor-bonded undercoat. Sand or mechanically remove all loose paint, clean and roughen smooth surface, and recoat.  
FISH EYES. Small holes in the coating film. Separation or pulling apart of wet film to expose underlying finish or substrate. Application over oil, dirt, silicone, or incompatible coating. Abrade back until contaminated area can be degreased, allow to dry and recoat.  
IRREGULAR SURFACE DETERIORATION. Deterioration at edges, corners, crevices, channels, etc. Difficult to coat surfaces; or configurations that permit collection of moisture, salt, and dirt. Round edges, fillet weld seams and crevices; avoid configuration that permit collection of contaminants; provide drainage.  
  LIFTING OR PEELING. Paint lifting or peeling from surface. Poorly prepared surface. Incompatible overcoating. Moisture on the surface. Overcoating times exceeded. Remove loose coating, abrade, degrease and recoat in accordance with recommended specification.  
  LOSS OF GLOSS. High humidity, cold conditions and dew fall will cause the coating to cure with a low gloss level. Ultra Violet degradation over a period of time. Abrade back and recoat.  
MUD CRACKING. Deep, irregular cracks as with dried mud. A relatively inflexibile coating applied too thickly. Remove coating and abrasively blast steel before reapplying at lesser thickness; sanding/mechanical cleaning may be acceptable on older substrates.  
ORANGE PEEL. Hills, valleys in coating resembling of orange. Paint too viscous; gun too close to surface; solvent evaporated too fast; or air pressure too low for proper atomization. Before cure, brush out excess coating and modify spray conditions. After cure, abrade back to an even flat surface and recoat. If using a roller, it may be necessary to lay off using a brush or pad after roller application.  
OVERSPRAY. Also called dry spray. Dry, flat, pebbly surface. Particles reaching surface not wet enough to level because of too rapid solvent evaporation; gun too far from surface; or coating particles falling outside spray pattern. Before cure, remove by dry brushing followed by solvent wiping. After cure, sand and apply another coat.
PEELING OF THICK, INFLEXIBLE COATING. Peeling of thick paint from substrate. Stress from cured, weathered (contracted) coating exceeds adhesion to substrate. If limited, spot-remove loose coating and apply flexible coating; if extensive, scrape, gritblast, mechanically or chemically remove coating to substrate before recoating.  
PINHOLING. Tiny, deep holes exposing substrate. Insufficient coating spray atomization; coarse atomization; or settled pigment. If uncured, brush out and apply additional coat. If cured, appl additional coat.  
PINPOINT RUSTING. Rusting at pinholes or holidays. Pinholing or too high a steel surface profile for coating thickness. Use holiday detector for early detection of pinholes; apply additional coats after mechanical or blast cleaning.
  RUNS. Running of wet paint into uneven rivulets Paint has been over thinned. Too much paint applied. Abrade back to an even flat surface and recoat.
SAGS. Also called runs or curtains. Excess flow of paint. Spray gun too close to work; paint applied too thickly; too much thinner; or surface too hard or glossy to hold the coating. Before cure, brush out excess coating and modify spray condition. After cure, abrade back to an even flat surface and recoat.
UNDERCUTTING. Blistering and/or peeling of coating where exposed steel is rusting. Corrosion products formed where steel is exposed, undermining and lifting coating. Early detection of defects with holiday detector and correction; use inhibitive pigments in primer.
UNEVEN GLOSS. Nonuniform sheen, shiny spots. Nonuniform film thickness; moisture in film; temperature change during curing; or paint applied over soft or wet undercoat. Allow to dry and apply another finish coat under acceptable conditions for moisture and humidity.
WRINKLING. Rough, crinkled surface. Surface skinning over uncured coating because of too much thickness and/or too warm weather causing solvent entrapment (uncured paint) under the surface. Scrape off wrinkles and apply thinner coat; avoid intense sunlight.