Flakes, Cracks, and Crazing
What is it and how do I solve this?
This is when individual coatings or an entire paint system crack completely, or craze, creating a network of fine cracks. There many reasons why they happen, but with careful preparation before applying paint and following a few simple rules, you should be able to prevent it.
How to recognize it
Often called crazy cracking as it looks like a crazy paving walkway or a crocodile skin. Paint often curls up as it peels off the surface.
Causes and how to prevent them
- Build-up of coatings over long periods leading to internal stress.
Prevention: Ensure that coatings are applied to old paint systems which are in good/sound condition. - Maximum over coating times exceeded and correct preparation not carried out.
Prevention: Ensure that recommendations and guidelines are followed e.g. on labels, technical datasheets. - Incorrect coating scheme such as two pack over one pack or incorrect one pack over a two pack.
Prevention: Ensure that recommendations and guidelines are followed e.g. on labels, technical datasheets. Don’t mix systems. - Strong solvents used on or with conventional coatings leads to underlying paint being affected.
Prevention: Use correct solvents for wiping down or thinning products. - Aged / old antifouling paint not prepared correctly before new paint applied.
Prevention: Ensure that coatings are applied to old paint systems which are in good/sound condition. NEVER DRY SAND ANTIFOULINGS. The antifouling should only be wet sanded (if required) for health and safety reasons. - Paint coating applied too thickly leading to excessive shrinkage.
Prevention: Ensure that recommendations and guidelines are followed e.g. on labels, technical datasheets. - Substrate movement such as on GRP / composite boats with thin laminates and on planked timber vessels.
Prevention: Perhaps try using a single pack instead of a two pack. - Overcoating recommendations not followed or incorrect paint system applied e.g. incorrect primer used with antifouling.
Prevention: Ensure that recommendations and guidelines are followed e.g. on labels, technical datasheets. - Antifouling, especially hard types, left to build up over many years.
Prevention: Ensure that coatings are applied to old paint systems which are in good/sound condition.
How to treat it
- Scrape or sand loose coatings to a good firm edge and feather the edges of the intact coatings to give a smooth overlap. Wash it with fresh water to remove all contamination. Patch, prime and apply finish coatings as needed.
- NEVER DRY SAND ANTIFOULINGS. The antifouling should only be wet sanded (if required) for health and safety reasons.
- In some instances you may not be able to achieve a good firm edge and the whole coating and/or system may have to be removed.
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