Chemical Reactions in Underwater Lighting

A common question asked of us is "what light fixture should I buy for my fountains?" and "how much of a difference does having a fixture made of brass or stainless steel make over buying composite?" However, I think the more important question to ask is "how will this fixture hold up in my fountain or pond?". Most people don't realize that the normal chemicals they add to their pools or fountains are highly corrosive to underwater light fixtures (of any kind). Underwater lighting fixtures are vulnerable to high intensity acid-based chemicals, so please be aware that if placed in a pool or fountain with muriatic or other acid chemicals, your light fixture will slowly be eaten away at. This is NOT corrosion as corrosion is a reaction of metals with oxygen and brass and stainless steel are natural earth metals, cannot by very nature, corrode or rust. So to prove my point, I’m going to have to go into some chemistry, which I apologize in advance for. For those who just want a quick answer, here's what you came for: YOU CANNOT USE UNDERWATER LIGHT FIXTURES IN WATER THAT HAS BEEN TREATED WITH AN ACID BASED CHEMICAL. Brass is a composition of the metals copper (which is a native metal) and zinc (which is an anti-corrosion alloy). Native metals are found naturally on Earth in either pure deposits and/or in alloys, which consists of aluminum, antimony, arsenic, bismuth, cadmium, chromium, cobalt, indium, iron, manganese, molybdenum, nickel, rhenium, selenium, tantalum, tellurium, tin, titanium, tungsten and zinc. As such, they are immune to corrosion and rust because they do not react to oxygen, unlike materials such as iron. So when placed in normal (read as neutral pH 7.0) water, brass and stainless steel lighting fixtures will remain untouched. However, with the introduction of intense acids typically used in pools or fountains, brass and stainless steel will be eroded by the acid content of the chemicals and begin to separate back into its core elements (copper and zinc). What this means for the end user: Depending how strong of an acid you are using, your fixture will begin to dissolve at a given rate and will cut the usable lifetime of the fixture down by a signification percentage (50% or higher depending on the copper/zinc balance). To combat this, you will need to use pool/fountain chemicals that are rated for natural rocks/minerals (such as natural based algae chemicals). Stay away from anything that contains concentrated muriatic or nitric acid. If you insist on continuing to use those type of chemicals, you may need to consider using PVC or geo-composite underwater fixtures. However, even those type of fixtures will not last long being submersed in water with a high concentration of acid (you’ll be lucky if they last a year and it WILL also adversely ect whatever lamping you’re using). Final Word: When working with underwater lighting or even normally lighting in high humidity areas, the kind of material used in the lighting fixtures will be directly affected so you must choose carefully. Aluminum is a low cost material but it will corrode when exposed to high amounts of water and offers no protection from high concentration acids. Brass offers complete protection against rust and corrosion but will be slowly eaten by nitric and muriatic acids that are typically found in pool and fountain chemicals. PVC and geo-composite fixtures will be protected against rust and corrosion and will offer a fair amount of resistance to high intensity acids but will ultimately fail over a given period of time. So my best piece of advice is to remove the acid from the picture and use an eco-friendly alternative algaecide that won’t damage your lighting fixtures.