This is my first post in your forums and I must also say that y'all have an excellent site here. I heard about it because my wife (Michelle) works with Dawn and Sondra.
Anyways....
Couldn't help but to respond to this post and it may be a little lengthy to explain...I am in the industrial coatings business and what you are experiencing with your aluminum corrosion is due to a process called Galvanic Corrosion or Dissimilar Metal Corrosion. It happens when 2 different metals are in contact with each other and one sacrifices itself for the other. Zinc being the most sacrificial metal there is (hence the zinc on a boat motor to protect carbon steel parts) and Graphite and Platinum being the least sacrificial. If you are using Stainless Steel bolts to attach the poly and that bolt comes in contact with the Aluminum, the Aluminum will sacrifice itself for the Stainless. There is a triangle that must be present for this to happen 1) the metal join must be wet with a conductive liquid 2) there must be metal to metal contact 3) the metals must have sufficiently different potentials. Salt water is the worse because it is more conductive. Water travels up the threads and to the contact area and that is when corrosion takes place. Even morning dew can do this. As the water evaporates it becomes more concentrated and corrosion speeds up. All you will need to do is seal the exposed areas (top and bottom) with something like clear polyurethane, clear nail polish after the area is completely dry.
I don't know anything about the Steelflex you are referring to, but if it seals the water from getting to the metal contact point, that's why it is working.
Sorry to be so long winded. Hope this helps.
