Generally speaking, any door handle on backplate, door handle on rose, or door knob can be used outside. The most important factor to consider is the finish of the door handle or knob. In an outside environment, particularly where a door is exposed to rain, wind or sea air, the finish will tarnish at a quicker rate than if it were indoors.
Chrome, Nickel & Stainless Steel Finishes
As a general rule, chrome, nickel and stainless steel will fare better outside than other finishes, like polished brass. Save for a little spot of dusting, chrome requires minimal maintenance. A light coating of wax will maintain it beautifully for many years. As you may know, chrome is used extensively in bathrooms for this very reason. A particularly durable range of handles is available from lead supplier, Eurospec, who offer a range made from marine grade 304 or 316 stainless steel.
Polished brass handles and knobs are lacquered and the quality of this lacquer can vary greatly. If you want to use polished brass outside, go for a high quality, slightly more expensive handle as the lacquer will be better. However, it will tarnish over a period of a few years. In this case, the lacquer can be removed with paint stripper which will then expose the original brass, although you should be aware that this will then need continual polishing with a brass cleaning product. The original brass will also take on an 'antiqued' appearance when exposed to the air and will gradually change colour over a period of time. This can look very attractive if cleaned and maintained carefully. Indeed, many people choose to buy handles and knobs in unlacquered brass because they wish to get this effect.
PVD Brass Finishes
There are some polished brass products for use externally which have undergone a process called 'physical vapour deposition', PVD, which achieves a durable finish with a 25 year finish warranty. This state-of-the-art process deposits molecules of hardwearing metals onto the brass surface of the product. This microscopic layer protects the brass finish from discolouration, even when exposed to coastal areas, sunlight and pollution. This protective feature makes these products ideal for external use in normally high 'wear & tear' situations such as public buildings, retail establishments, hotels and commercial premises. This finish is perfect for the discerning individual wanting the peace of mind that their external door furniture will last and look good for many years, with minimal maintenance.
Black Antique & Rustic Finishes
Black antique and rustic handles and knobs should be used carefully in an outside environment as they will show signs of rust fairly quickly. If frequently maintained with a good coating of wax, this will slow the process down. However, sometimes the natural rust effect on these products adds to the appeal, which makes this is a very personal choice.