Flaking, Cracking, 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.

1. 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.
2. 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.
3. 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.
4. Strong solvents used on or with conventional coatings leads to underlying paint being affected. 
   Prevention: Use correct solvents for wiping down or thinning products.
5. 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.
6. Paint coating applied too thickly leading to excessive shrinkage 
   Prevention: Ensure that recommendations and guidelines are followed e.g. on labels, technical datasheets.
7. 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.
8. 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.
9. 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.