Our top 6 tips for Structural Glazing adhesion

Tip One- Mill Finish Aluminium

Mill finish aluminium is not a suitable substrate for structural silicone bonding due to unpredictable adhesion as a result of production processes and possible long-term corrosion.

Tip Two- Anodised Aluminium

Anodised aluminium with an aluminium oxide layer thickness of >15 mm and preferably complying with QUALANOD requirements is an ideal substrate. The anodising samples supplied for Sika to test must of course be fully representative of those used for the project. If in any doubt it really is best for peace of mind to carry out another test. Anodised aluminium components must be protected during storage to prevent any contamination which could affect subsequent adhesion. The anodised profile manufacturer may provide a ‘shelf life’ for the treated material and if this time is exceeded then additional adhesion testing should be undertaken to verify its suitability.

Tip Three- Polyester Powder Coated Aluminium (PPC)

Polyester Powder Coating formulations can vary from manufacturer to manufacturer and consequently could impact the adhesion of the structural bonding system. The powder coating must provide in-service durability and performance to match or exceed the intended lifetime of the aluminium profile and must approve the coating for the use in structural glazing facades. As well as the quality of the polyester powder coating formulations, the oven parameters could adversely affect the quality and performance of the coating. Variation in oven temperature and the time spent in the oven may have a detrimental effect on the cure of the paint. This could impact the cure of the paint for structural applications.

Tip Four- Stainless Steel

Stainless Steel has been widely used and is an excellent substrate to bond to as it does not suffer from surface corrosion. Typically, 316 grades are used for structural bonding. The surface finish is crucial for the successful bond and must not be changed after testing.

Tip Five- Ferrous Metals

Galvanised steel or painted ferrous metal substrates should not be considered according to ETAG 002, due to their potential corrosion when exposed to environmental factors. If the galvanising or paint is damaged, the ferrous metal will corrode and undermine the performance of the structural sealant.

Tip Six- Glass

With the exception of float glass, all other glass types e.g. Low E Glass, Pyrolytic Coatings, Ceramic and Enamel Coated glass must be tested on a project basis to confirm the adhesion of the structural and insulated glass sealants to these surfaces. Confirmation of the specified glass type and its suitability should be obtained from the glass manufacturer for structural glazing projects. Edge-deleted low E coatings require special care as the processed surface must be completely removed to leave float glass as the bonding substrate. The adhesion on such representative samples must be tested prior to the IG production. The edge-deletion process parameter must not be changed after the testing.