Surface Treatment Prior To Bonding
In virtually every application the quality of the bond between the resin system and the surface to which it is applied is improved if the surface is clean and dry.
This is particularly true of adhesive applications where stress will be applied to the cured bond line.
It is also true where protective coatings are used. The following surface preparation procedures are recommended.
Degrease – Wipe laying surfaces with Methyl Ethyl Ketone (MEK) or acetone to remove all oil, dirt, and grease.
Etch – For optimum results, metal parts should be immersed in a chromic acid bath solution consisting of:
- Sodium dichromate – 4 parts by weight
- Sulfuric acid – 10 parts by weight
- Water – 30 parts by weight
The solution should be held at a temperature of 160°F (71°C), and the parts left immersed for 5 to 7 minutes.
Rinse – remove metal parts from etching bath and rinse in clean cold water (de-ionized water is recommended). If thoroughly clean, metal surfaces so treated will hold a thin film of water.
Dry – To accelerate drying, items to be bonded can be placed in an air-circulating oven.
Degrease, scour and dry – Often etching as outlined above is not practical. The metal surfaces may be cleaned by degreasing as noted above, scouring with an alkaline cleanser followed by rinsing and drying.
Degrease and dry – Degrease the surface as noted above, sand or sandblast the surface lightly but thoroughly. Rinse with acetone or Methyl Ethyl Ketone (MEK), and dry.
Degrease – With MEK as above, or with a strong boiling solution of a good grade household detergent.
Etch – For optimum results, degreasing can be followed with the chromic acid bath outlined above.
Sand – Bonding surfaces should be sanded lightly, but thoroughly to remove all external contamination.
Clean – Carefully remove all dust, or particles of wood from sanded areas. A stiff and clean brush, or compressed air can be used.
Clean – Remove all dirt, oil, or other surfaces contaminate with detergent sop or degreasing solvent and water, followed by thorough rinsing and drying. A solvent that does not have a detrimental effect may also be used.
Sand – Surfaces to be bonded should be sanded lightly, but thoroughly to remove surface sheen.
Clean – Carefully remove all dust or particles of plastic from the sanded area. A clean brush, lint free cloth, or compressed air may be used.