Corrosion Prevention

Most panel bonding and direct glazing applications involve use of steel, aluminium or zinc containing metals which are vulnerable to corrosion if untreated with a suitable anti-corrosive coating system.

Corrosion of bonded metal surfaces will cause deterioration of adhesion between the metal and Sikaflex adhesive that can ultimately lead to bond failure. Therefore it is imperative to reduce the risk of corrosion of bonded parts, where possible.

Corrosion is the process of converting metals from their artificial metallic form to their natural oxide/salt form and can only occur if water and oxygen are in contact with metal surfaces.

The use of a suitable anti-corrosive paint coating system (primer and topcoat) correctly applied over exposed metal surfaces, provides an effective method of corrosion protection. Care should be taken to ensure complete encapsulation of the metal components with each component of the coating system, to ensure it's effectiveness.

Sharp edges, corners or weld seams of metals should be rounded off or ground down before coating. If they are left they will create potential weak points in the corrosion protection system.

When panel bonding / direct glazing, it is also crucial to apply the Sikaflex adhesive bead, of suitable dimensions, continuously around the entire perimeter of the panel/window and ensure the two bead ends meet. This will ensure that water reaching the outside edge of the adhesive bead can't penetrate and remain within the panel cavity.

Water entry via use of spacers and setting blocks is possible during bonding and glazing applications. Care should be taken not to cause discontinuity of the adhesive bead, creating risk of water penetration, when using such items.

Mechanically fixing two dissimilar metals will result in corrosion. This process is accelerated if water comes into contact with the joints. The use of an electrically non-conductive Sikaflex adhesive to bond these metals instead, will not allow this type of corrosion to occur.

To ensure complete corrosion protection, always use the full anti-corrosion paint system on the entire substrate. Do not substitute adhesive or adhesive primer as a suitable corrosion barrier over corrosion resistant paint system. Suitable corrosion protection for steel and aluminium includes a fully painted surface, electro-coated surface or primed surfaces if the primer is a suitable corrosion preventative coating and it is applied correctly in terms of film thickness and eveness of coat.

It is important to test the adhesion of substrate coatings with Sika Adhesives. If only one layer of the paint system is changed, the testing has to be done again. All substrates should be tested by giving samples to your local representative to be tested by Sika's Technical Department.

Click below to view Information on
- Bond Line Dimensioning
- Corrosion Prevention.
- Handy Trade Tips
- Joint Design for Direct Glazing Applications.