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February 29, 2020
Occasionally we get pictures sent to us from customers depicting stainless steel pool light rims which have become discoloured. Some look like rust and others look as the though the shiny chrome finish has vanished. Often times this happens very quickly, sometimes within 12 months of installation. We have seen examples of this affecting every product type, brand and manufacturer.
There are two things going on when this happens. The problem typically starts with electrolysis (which is not in itself abnormal) which then triggers a galvanic corrosion process. What should be a very slow process (decades) speeds up to years/months. The amount of stray current and chemical/salt content of the pool greatly influences the speed of this process. The more salts in the water, the faster it breaks down the metals. Below is a chart showing speed by metal type.
In most pools this process isn't even noticeable. But when grounds/sodium/current/re-bar/etc go bad, it becomes glaringly (or non-glaring, pardon the pun) obvious. Essentially your pool becomes a giant battery like the image depicted below. Anything metal in your pool is the red part, or anode side. As the ions pass, the metal breaks down.
In addition to lights, if the pool has metal hand rails or ladders it also affects them the same. See pictures and description below as another example.
This new ladder was installed in a saltwater pool with a broken/non-existent bonding grid. Within a week the ladder had blue streaks that looked like it had been struck by lightning. Another week later the ladder was completely black despite the existence of an inline sacrificial anode as well as anodes bolted directly to the ladder. The ladder was replaced and within another week, it also turned black.
Often times, but not always it involves a salt water pool. Bottom line is this, if you are experiencing this, there is no easy answer or cure. More importantly the problem is not the metal in the pool but a much bigger issue that requires a deeper understanding of the problem and solution. While there are several possible causes of this phenomena, these are the top ones:
The easiest and cheapest way to start solving the problem is using a 4-5 foot solid copper grounding rod purchased from your local hardware store, very inexpensive. Hammer it into the ground, so about 1 foot is exposed. Put this as close to the transformer as possible. Hook the pool light ground to your new "Rock Solid Copper" rod in the "Ground". Isolate the issue first. Where and from what direction the stray current is coming from is hard if not impossible to determine. Happy rabbit hole hunting.
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