I have an in ground salt water spa which is approximately 10x10. It is 18 months old and has a stainless steel main rail that is anchored in the decking and at the bottom of the stairs (under water) and a stainless steel exercise rail at the deep end of the spa (it is sloped from three feet to four feet deep) that is totally under water.
Almost from the beginning, the stainless steel that is submerged is getting a black film (that can be wiped clean) that I believe is galvanic corrosion, but my builder is struggling to comprehend that.
To give more detail, the main rail is held in place by bronze inserts that are cemented in the ground. I understand this is common construction. The exercise rail is held in place with six bolts of undetermined material.
When we disconnect the rails from their mounts and simply lay them in the spa, the stainless steel remains clean. The bolts also remain clean. However, the ground wire that is connected to one of the bolts continues to get the film. An electrician did come out and determine that the spa is grounded properly.
So my theory is that since the bolts remain clean and the stainless steel when disconnected remain clean, the bolts may be causing the galvanic corrosion of the weaker stainless steel and ground wire.
Any guidance would be greatly appreciated. And if I am correct, what should the bolts be made from to stop this from happening.
Thanks in advance.
Almost from the beginning, the stainless steel that is submerged is getting a black film (that can be wiped clean) that I believe is galvanic corrosion, but my builder is struggling to comprehend that.
To give more detail, the main rail is held in place by bronze inserts that are cemented in the ground. I understand this is common construction. The exercise rail is held in place with six bolts of undetermined material.
When we disconnect the rails from their mounts and simply lay them in the spa, the stainless steel remains clean. The bolts also remain clean. However, the ground wire that is connected to one of the bolts continues to get the film. An electrician did come out and determine that the spa is grounded properly.
So my theory is that since the bolts remain clean and the stainless steel when disconnected remain clean, the bolts may be causing the galvanic corrosion of the weaker stainless steel and ground wire.
Any guidance would be greatly appreciated. And if I am correct, what should the bolts be made from to stop this from happening.
Thanks in advance.
A couple years ago I made the mistake of connecting my water heater copper flex lines to some galvanized metal pipes. In two years they were almost corroded shut inside. Not my finest hour. 
