I'm looking for the best way to prevent corrosion between the underside of the T track when fastened to horizontal surfaces (coach roof and toe rail).
When I removed the genoa tracks, I found a lot of corrosion to the underside of the T track (not apparent when looking at the top of the track), mostly around the bolt holes. The corrosion was so deep in many parts that had to scrap those and buy two new 10' sticks. I understand the problem of SS fasteners and aluminum and that looks like most of the issue was lack of tefgel during original installation, but there were some corroded spots that were between bolt holes.
I also removed some 4' pieces of T track from the coach roof that I installed about 3 years ago and saw some, but very little corrosion (it was only 3 years ago when installed)
The coach roof tracks were through bolted (flat head machine screws) and bolt holes bedded with butyl (including butyl around threads and under bolt head) There were no leaks into the cabin through the coach roof tracks (removed the core around each bolt hole and filled with epoxy).
What I found with the coach roof tracks is that the force of tightening the 5/16 bolts (every 4") caused the edges of the track to compress the fiberglass coach roof outer layers. That is not a big deal, except it looks like in a couple of spots the compression formed a dam and prevent water from draining out, leading to the minor corrosion (T tracks are concave on underside surface). Over time, this would lead to more-than-minor corrosion. This corrosion was between bolt holes and the adjacent holes had no ss/aluminum contact (I used butyl on threads and underside of bolt heads).
I did not put any butyl between bolt holes, just donuts encircling the bolts when I installed the coach roof tracks 3 years ago.
When I rebed all the tracks, they are all going to be on fiberglass (I'm not replacing the teak caprail). What is the most effective way to prevent water from pooling underneath the T track when fastening to a horizontal surface (or promoting water drainage)?
The other question centers on the interface between the bolts and the aluminum track. When bolting with butyl, I countersunk the fiberglass holes, placed butyl donuts around the portion of bolts that extended below the track and put some butyl around the bolt head and threads that contacted the aluminum in the 4"-on-center holes. Problem with this is that, although the buytl prevented water intrusion through the deck, the tightening of the bolts pressed all the butyl out from between the heads and the countersunk aluminum (underside of head, top of track). This lead to some SS/aluminum corrosion in a few of the holes. There were also a couple of the 4" holes in the track that had a continuous layer of aluminum oxide, were there was direct contact between AL and SS.
Has anyone used butyl between the track and the deck, but used tefgel where the SS bolt contacts the upper part of the track (underside of bolt head) and where the bolt passes through the track to prevent SS/AL corrosion?
Thanks
I haven't re-bedded my tracks (yet), but this video shows someone that applied butyl to the entire bottom of the track. It doesn't look like they used TefGel under the bolt heads. It also explains how they dealt with some corrosion on the bottom of the track before they reinstalled it.
https://www.youtube.com/watch?v=IQlXZDJEthQ&index=35&list=PLoE3FmplhAXNsNWWZ6iTMzYYwKVtDanCr&t=566s
Hope this helps.
Chuck