Trade Secrets: Ensuring clean surfaces makes for a strong epoxy bond
When it comes to preparing a surface for epoxy application, the cleaner you make the area the better the outcome will be – any sort of contamination on the surface will likely result in reducing the adhesive power of epoxy.
Surface roughening improves the strength of the adhesive bond by enabling the epoxy to mechanically ‘key’ into the surface.
To ensure your epoxy bond is strong and durable, your surface must be clean, dry and thoroughly abraded. Surface roughening improves the strength of the adhesive bond by enabling the epoxy to mechanically ‘key’ into the surface.
There are a few simple precautions you can take to protect against contaminants on the surface.
What should I watch out for?
You – Your body creates oils to protect and waterproof your skin, much like marine epoxy does for your boat. It’s normal when working with epoxy to want to run your hand over the surface to check its smoothness. Don’t do this unless you are wearing a clean glove, otherwise your skin will contaminate the surface.
Sanding Dust – The best steps to follow for removing sanding dust are: use a vacuum, use an uncontaminated brush to sweep it off or use water to wash it off.
Organic Solvents – These can react with other elements and leave deposits on the surface that can affect adhesion. If you need to use a solvent, use plain white or unbleached paper towels to apply the solvent. Then use clean paper towels to wipe it off whilst it’s still wet. Make sure you regularly change paper towels and do not use rags.
Compressed Air – These can contain their own oils and water that can contaminate the surface.
Heaters – Some heaters, such as Salamander heaters, do not burn cleanly and can in fact produce lots of moisture that may collect on the surface.
Zinc Stearate – This is a chemical that can be found in some types of sandpaper. Just using it can contaminate a surface. We recommend that you use aluminium oxide or non-stearate treated waterproof wet/dry sandpaper instead.
Amine Blush – Many organic solvents will not help you remove blush. Instead, wash with clean water and use a Scotch Brite pad and dry with paper towels.
How do I know the surface is clean enough?
Wash it with water. If the water channels or beads in certain areas then you need to repeat the cleaning process. However, if it sheets off the surface evenly then the surface area is ‘clean’ and ready for application.
It’s a good idea to keep this list of causes of contamination by your side when preparing your next surface for epoxy.
It’s a good idea to keep this list of causes of contamination by your side when preparing your next surface for epoxy. If you want further information, then head to West System International for many more surface preparation techniques.
Our thanks to Brian Knight for his great ideas on how to avoid surface contamination.