Coating Failures and Defects Guide.pdf

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Coating Failures and Defects
A Comprehensive Field Guide
Corrosionpedia.com in partnership with Fitz’s Atlas 2 and ASM Handbook Volume 5B
Coating Failures and Defects
Brendan Fitzsimons
Trevor Parry
Brendan Fitzsimons is the author of the original Fitz’s Atlas as well as the
Fitz’s Atlas 2. Brendan has been in the protective coatings industry for over
25 years working for Inspection and Consulting Engineers, Paint
manufacturers, major oil and gas suppliers and International Coating
Contractors working in the marine, offshore and infrastructure industries.
Brendan is a Chartered Scientist, a Masters Degree in Materials
Engineering, NACE Protective Coatings Specialist and a NACE Coating
Inspector and Peer Reviewer. Brendan is also a Fellow Member of the
Institute of Corrosion.
Trevor Parry has over forty years experience in the protective coatings
industry and principally involved in the evaluation of paint coatings, their
modes and mechanisms of failure, cause and extent of breakdown and
recommendations for their remedial treatment. UK appointed expert to
International Standards Organisation committees and numerous
involvements as Expert Witness in High Court, Arbitration and Mediation
on the subject of paint coatings.
Trevor is a Chartered Scientist, Chartered Chemist, Fellow of the Royal
Society of Chemistry, a professional member of the Institute of Corrosion
and a member of NACE, and a supporting member of the London Maritime
Arbitrators Association (LMAA).
Coating Failures and Defects
Overview
Coatings are a complex combination of raw materials that must be mixed, applied to a prepared substrate, and dried and cured correctly to perform to
their maximum capability. They must be able to be applied in diverse environmental conditions and then be expected to protect the substrate from the
damaging effects of rain, sunlight, wind, heat, cold, humidity, and oxygen in various combinations and cycles and still retain their integrity and often their
aesthetic qualities. Some coatings, such as those applied to ships, also must be resistant to abrasion, in the case of cargo hold coatings, and cyclic changes
of chemicals and tank cleaning, in the case of tank linings. Therefore, it is not surprising that those coatings can suffer from premature failure and/or
exhibit defects that may or may not result in failure. It is not generally straightforward to establish the reason for the failure of a coating due to the many
potential factors that may be involved. These could include formulation, surface preparation, application, drying and curing times and conditions, and
environmental exposure, with more than one contributing factor often being involved.
Failures and defects can manifest themselves at various times in the life of a coating. Prior to application, they can take the form of settlement and
skinning, during application as runs and sags, shortly after application as solvent popping and orange peel, and during service as blistering and rust
spotting. To determine the cause and mechanism of coating failure, all possible contributory factors must be evaluated together with a detailed history
from the time of application to the time the failure was first noted. Many coating failures require further evaluation and analysis to be carried out by a
qualified chemist or coating specialist, often using specialized laboratory equipment.
Most of the following examples of failures and defects, together with descriptions, probable causes, and suggested preventative measures, are
reproduced by the kind permission of Fitz’s Atlas 2, although some photographs have been included from other sources. Fitz’s Atlas 2 contains sections on
welding faults, surface conditions, marine fouling, and microscopy in addition to the main section of 237 photographs of coating defects and failures in 93
separate categories.
Coating Failures and Defects
Abrasion
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 ship.
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.
Fig. 1 The mechanical action of rubbing, scraping, scratching, gouging, or erosion.
Coating Failures and Defects
Adhesion Failure
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.
Fig. 2 Paint fails to adhere to substrate or underlying coats of paint.

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