To the point only austenitic will do for aluminium

Customers love aluminium windows and doors because of their engineered quality and great looks. But this quality is completely undermined if the wrong fasteners are used in their fabrication.

Despite representing a tiny part of the finished product, fasteners have a huge impact on performance. If you’re fabricating different materials under one roof – such as PVC and aluminium – take extreme care. Using any old screws in aluminium is a no-no if you want to ensure reliable window and door performance.

Fasteners mainly come in coated carbon steel and several types of stainless steel with different levels of corrosion resistance. But for aluminium windows and doors, the only choice is austenitic stainless steel screws (sometimes referred to as A4 or grade 316).

The reason lies in metallurgy. Think of how batteries work – different metals react with an electrolyte to generate an electric current until the metals eventually corrode to nothing and the battery runs flat. A similar reaction (galvanic corrosion) takes place when certain metals are combined. One metal corrodes preferentially when in contact with another in the presence of an electrolyte – with aluminium windows and doors that electrolyte is water.

The extent of galvanic corrosion depends on the metals being combined. In short, inserting carbon steel or martensitic stainless steel into aluminium could result in a far quicker corrosive reaction compared with that of aluminium and austenitic stainless steel.

So austenitic is the only choice, but does its lack of magnetism make fabrication trickier? Not the case when an AC2 driver bit is used in a well-formed screw recess. Available from Rapierstar, this provides a better hold on the screw during fabrication for greater production efficiency.

Using alternative screw types is very risky. A martensitic drill point, or a bi-metallic fastener, could result in premature failure of the screw.

Specifiers understand the reason for using austenitic fasteners in aluminium fenestration, so failure to manufacture to the spec will mean costly consequences sooner than you think. The galvanic process could result in hardware becoming loose or detached and windows or doors no longer functioning properly. That means expensive call-backs, particularly for high rise commercial buildings where safe access and user disruption need to be managed and budgeted for.

More costly is the long term reputational damage to your business. Online reviews, word of mouth and law suits all affect businesses that fail to deliver. Is it really worth the risk to save a few pounds?

Using austenitic stainless steel fasteners in aluminium fenestration is the only way to give your clients a credible warranty. In the case of Rapierstar, that’s a 10-year guarantee on the fastener performance.