Approximately 3 million people in the UK (out of 60 million) live on the coast. For them, marine corrosion is a daily battle, most commonly manifested in the form of rust. So, what is marine corrosion? Sometimes known as sea corrosion, or salt spray corrosion, Marine corrosion is defined as the accelerated deterioration of metal and other materials, caused by a reaction with the salt-heavy atmosphere of a coastal environment.
Salt-spray and atmospheric salt-content seen in coastal areas is incredibly destructive to many metals, and other materials. While salt-spray is at its most destructive on the seafront, atmospheric salt spray corrosion can occur several miles from the sea due to wind spread and other factors.
Research has shown that corrosion of exposed steel on the coast can be 400-500 times greater than the same steel placed in the desert. Whilst marine corrosion is effective up to several miles from the sea, the destructiveness of salt spray is exponentially greater nearer the ocean. One study found that steel samples located 24 metres (80 feet) from the coastline corroded 12 times faster than those 243 metres (800 feet) from shore. To help explain how much of a cost marine corrosion extolls on people who live and work by the sea, the National Association of Corrosion Engineers has estimated the repair, maintenance, and replacement cost of marine corrosion worldwide at between $50-80 billion a year.
As architectural ironmongers, at More Handles we are often asked about how to prevent marine corrosion, rust, and atmospheric pitting in door handles and other door furniture. By their nature, door handles, door knobs, pull handles and push plates, bell pushes and letter plates must be used on the exterior of a house or other building, and so are very susceptible to marine corrosion. In seaside towns and cities, this corrosion can take a terrible toll on exterior metal products. So then, how does a homeowner battle this aggressive form of corrosion? As with many things, prevention is better than a cure. When a customer asks what steps they can take to avoid salt-spray corrosion, we would tell them to choose their door furniture based on what materials are resistant to sea corrosion.
While no manufacturer can guarantee their finishes for external use due to vastly changing atmospheric factors, it is a fact that some metals and finishes are naturally far superior to resisting corrosion than others. Lets take a look at some basic rules to remember when choosing door handles for use outside by the sea.
1) We strongly recommend choosing materials that don’t have a plated finish, such as Solid un-lacquered Brass, Solid Bronze, and Solid Pewter door furniture. These three materials are the most impervious to decay in an exterior and coastal environment, the reason being, they are solid, not plated. While they will accrue deposits from salt-spray, they will not corrode in a destructive or aesthetic way, and can all be cleaned up quite easily. As these are not plated finishes, there is no plating to corrode and so the products are far more stable for exterior use, even in coastal environments. Therefore, we recommend customers consider using one of these materials if they live by the sea.
2) Avoid lacquered Brass. Choose only Un-lacquered Brass for use outside. Lacquer is a thin varnish coating applied to solid brass, ostensibly to prevent the brass from dulling down due to oxidization. The problem is, when used externally (especially by the sea) the lacquer coating is attacked at an incredible rate by atmospheric particles. When a lacquer breaks down, the first signs are black pitting marks and small black spots. These will eventually spread all over the item, and look very unsightly. We have seen even the best quality lacquers available deteriorate in a matter of months or even weeks when used by the sea. Salt spray really is that corrosive. What is the solution to this? Quite simply, Use brass that is not lacquered. Unlacquered brass will dull down faster by the sea, but the effect will be an antique one, rather than unsightly black pit marks. At More Handles, we carry a huge range of unlacquered brass ironmongery in different styles.
3) Ensure that your ironmongery uses a Solid Brass base metal. When purchasing Polished Chrome, Satin Chrome, and Satin nickel door furniture, remember that the base metal below these plated finishes makes a big difference in how long they will last when used outside. Manufacturers plate these finishes onto two base metals – Zamak and Solid Brass. Zamak should never be used externally, and if this base metal is used by the sea, the nice new plating will pit and crumble off in a matter of weeks. Solid Brass is a very stable base metal to use, but remember, when using plated finishes by the sea, there is always a risk the finish may corrode due to the destructive particles. Generally, it is accepted that Polished Chrome finish plated onto Solid Brass from a reputable manufacturer is the most durable of all plated finishes. Take a look at the DL range from Carlisle Brass, and the SZS range from Serozzetta for two excellent ranges of solid brass-based hardware, which have quality chrome plating. Click here to read more about comparing Solid Brass and Zamak when choosing door handles.
4) Remember that Stainless Steel is not always ‘Stainless’. Stainless steel is protected from corrosion by a thin layer of chromium oxide. Stainless Steel is available in several different grades. It should be noted that none of them are rust-free; they are only rust-resistant in varying degrees. The most common grades of stainless steel used in architectural ironmongery are Grade 201, Grade 304, and Grade 316. Grade 201 and 304 should never be used externally, as they will certainly rust. Grade 316 can be used outside in most situations, however when used in a coastal environment, surface rust may occur. Regular cleaning of Stainless Steel is absolutely essential to keep it corrosion-free
5) When using Black ironmongery, be careful not to scratch or knock the paint. Black Ironmongery is generally powder-coated, which is basically a painted finish. This can be used in a coastal environment, but be aware that the material beneath the coating is usually cast iron or wrought iron, and sometimes steel. these materials are extremely susceptible to rust. It is vital that when fitting these items, care is taken not to chip the powder coated paint finish, especially on the screw heads, as this will result in rust streaks and corrosion. If chips do occur, they should be touched in with black paint. More Handles stock a black touch up paint pen by From the Anvil, which is an excellent solution for any chips or scratches that, may occur during or after fitting. We recommend this touch up pen to customer who is purchasing black hardware, especially when it is going to be used in a coastal environment.
6) Consider PVD Brass finish. PVD Brass is a revolutionary finish that is impervious to damage in normal use including corrosion, oxidation, wear and abrasion. An abbreviation from Physical Vapour Deposition, the process involved in PVD manufacture is complex and includes an advanced vacuum treating process in which evaporated metal in a mixture of reactive gases is coated onto a stable base - either chrome plate or stainless steel. The procedure is long and the end result is expensive to produce, but the result is a finish that is ideal for exterior use, even in a coastal environment.
Let’s take a look at some of the most common finishes available for architectural ironmongery, and assess whether they are suitable for exterior coastal use.
Solid Brass: YES if unlacquered, NO if Lacquered.
PVD Brass: YES
Satin Chrome: YES if used on a solid brass base metal, NO if used on a zamak base metal.
Satin Nickel: YES if used on a solid brass base metal, NO if used on a zamak base metal.
Antique Brass: YES if the finish is created by natural oxidization, NO if it is a plated finish.
Black Ironmongery: YES but with care and maintenance
Wood and Timber: YES but with care and maintenance.
Stainless Steel: Grade 316 only, regular cleaning essential.
Solid Pewter: YES
Plain Cast Iron: NO
Glass: YES, but be aware of the base metal of the rose or backplate.
If you’re looking for door furniture with a Brass substrate, we carry many fantastic products that may be of interest. Our Heritage Brass V Rangecomprises Brass-based Door handles, Door Knobs and accessories in many different finishes. For modern Lever-on-Rose handles with a Solid Brass base metal, take a look at the Carlisle Brass SZM Lever Handle Range, and the DL range from Carlisle Brass.
As always, good cleaning and maintenance routines will prolong the life of any external ironmongery, especially when used in a coastal environment. Remember that the reason that items such as ironmongery decay is because of surface contact with destructive airborne particles. These particles can be removed with a cloth and mild soapy water. We recommend that this is done regularly in a coastal environment. In addition to this good regular cleaning routine, wipe over the surface with a lightly oiled cloth. Moving parts should be lightly oiled occasionally with ‘3 in 1’ oil or similar. This will prevent abrasion and extend the life of any external ironmongery.
If you need any further advice on what particular products are suitable for use by the sea, what type of handles and finishes you should look at, or would like to further discuss maintenance routines in coastal areas, please do not hesitate to contact our experts at More Handles HQ in Carlisle, Cumbria. We will be pleased to talk you through the technical aspect of getting the most out of your choice of ironmongery, and help you choose the right product to fit both your tastes and your seaside location!
TEL - 01228 516 516
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