Why use a stainless steel fastener?
1. Securing wood
Whether you are fixing decking, cladding or constructing buildings the wood contains water, tannins, pigments, oils and when in contact with a metal fixing corrosion begins. Adverse conditions (e.g. moisture in the air, acidic rain, salts, chlorine, higher temperatures) can accelerate the process and lead to discolouration around the location, and/or failure of the fixing along with deterioration of the wood in contact with the fixing. Stainless steel has properties that resist the corrosion process and hence are favoured by Carpenters, Joiners, Architects and Engineers. The rate at which acetic acid is liberated depends on the chemical constitution of the wood from which it is derived. This varies with species and largely accounts for the considerable differences in rates of production of acetic acid between timbers. Hardwoods are more prone to the natural releasing of acetic acids e.g. Oak, Cedar, Redwoods, Sweet Chestnut and Douglas Fir. In practice, kiln dried woods are much more likely to cause corrosion than air dried woods.
2. Securing metal
Stainless steels are often selected for their corrosive resistance and good practice recommends continuity of material type with the fastener to ensure fit for purpose and longevity of service life. Stainless steel is less prone to corrode than carbon steel or aluminium making it the preferred choice. They are also suited to fix other metal types (e.g. aluminium sheets, steel pipes) but working environments can cause bimetallic (galvanic) corrosion and movement can cause galling (“welding”) so other precautionary measures maybe required.
What grade is best?
There are a multitude of types and grades of stainless steels. Since the microstructure of stainless steels has a decisive effect on properties, stainless steels have been divided into types depending on their microstructure at room temperature; Ferritic, Martensitic, Duplex and Austenitic. The addition of different elements during manufacturing creates the different types and grades. Most popular and readily available for fasteners is A2 austenitic stainless steel (also referred to as 18/8, 304 and EN 1.4301), this grade has a typical composition of 18% Chromium and 8% Nickel. For use in harsher environments, e.g. coastal, chemical, A4 also referred to as Marine grade, 316, EN1.4401, which has the element Molybdenum added is more suitable as the addition provides further resistance to corrosion.
What makes stainless steel so special?
Stainless steels form a self protecting oxide layer when the right amount of chromium is added during manufacture. This layer self repairs in both dry and wet atmospheres without the need of costly painting, cleaning or maintenance. Improvements in manufacturing allow different amounts of elements to be added accurately to create this incredibly versatile alloy.
Is stainless steel expensive?
Compared to Carbon Steel fasteners, Stainless are typically of higher value. However as global production increases and Nickel prices remain low, the A2 stainless steel offers incredible value for money. The element Nickel is an important constituent of the alloy and historically been a cause of price volatility. Global markets dictate exchange rates, import tariffs, transportation costs, alloying element costs, production capacity and supply volumes; all factors determining the price of stainless steel.
Is stainless steel really “green”?
Yes, of all the mainstream metals and alloys available today, stainless steel is regarded as probably the most recyclable, sustainable and environmentally friendly metal on the planet.
FREQUENTLY ASKED QUESTIONS- STAINLESS STEEL
Is stainless steel magnetic?
Stainless in general tends to be LESS magnetic than "ordinary" steel, and some grades are non-magnetic. Stainless steel bolts can become slightly magnetic when processed by cold working. Even though the "raw material" going into the bolt making machine is non-magnetic, the process of forming the head and threads may cause the bolts coming out of the machine to be slightly magnetised.
Where should you use stainless?
There are three main geographical areas: Coastal, Industrial and Urban. Interestingly, coastal conditions in Great Britain can be found up to 10 miles inland. Industrial areas are usually self-contained within the manufacturing plant and specified within the construction and maintenance schedules. Urban areas especially near roads suffer from traffic pollution and salt from de-icing roads that can travel in the wind and attack buildings, bridges, tunnels, facades, cladding etc. Constructions 200m away from a busy road and 12 storeys high have been found to suffer measurable chloride corrosion.
What markets use stainless now?
The Food, Drink, Pharmaceutical and Chemical industries have utilised the benefits of stainless steel for many years for reasons of cleanliness, resistance to chemicals, preventing contamination and ensuring the quality of our daily drinks, food and drugs. Likewise the Oil, Gas and Marine industries are reliant on stainless steel to survive the harsh conditions of exploration and distribution of fuel and transport around the globe. However with the development of supply chains and logistics, Stainless Steel fasteners are now more readily available to the public and professionals via multiple outlets, no longer is it to be considered as a specialist product.
Where can I find examples of stainless steel?
The Chrysler building is probably the most famous of all the landmarks for its use of stainless steel, erected in 1930 in New York, it has only been cleaned 3 times and is still in perfect condition. The North Sea oil and gas industry has been built on the reliability of stainless steel in oil rigs and pipes. Every kitchen and restaurant will be full of stainless screws holding pipes, tables, sinks and toilets in place. New air conditioning units contain stainless steel filters to prevent bacteria growth. The internet and social media has an ever growing array of images and projects that are underpinned by stainless. Check out the horse heads (the Kelpies) in Falkirk.
Are there any downsides to stainless steel?
Not many! Compared to Carbon Steel fasteners it is softer and so pilot holes are recommended for wood screws in hardwoods whilst bolts need to be tightened slowly and less, preferably with some lubrication to reduce galling. Torque setting tables and torque wrench tools are highly recommended. As with most things in life, better products cost more.
Other factors driving the uptake of stainless?
Stainless steel is particularly suited to large-scale installations in segments of the commercial and public sector, such as hospitals, childrens homes, sheltered housing, prisons, schools and hotels; in other words anywhere there is a health & safety issue.
What lessons have we learnt?
New houses now use stainless steel wall ties to prevent walls from collapsing; bridges are now repaired using stainless steel rebar and stainless steel lath, and beading is now standard for cement based rendering of external walls. The cost of maintaining and servicing far outweighs the initial build cost when you consider a 50-100 year lifespan. Corrosive environments are common in industrial, coastal and, unfortunately, increasingly so in cities.........the future’s bright, the future’s stainless.