Originally Posted by DaveOnCudjoe
In the case of the Mac 36 the ends of the tubes are open and the corrosion
was evident in the bottom of the tubes. I have seen corrosion
in 6061 T6 which is a recommended alloy if not annodized. Dave
Sorry Dave I did not mean to cast doubt on what you have seen, but I think there will be some cause, such as stray current
from an anchor winch
Saltwater on its own will not corrode marine
grade alumium (even 6061 which is less corrosion resistant than the 5 series, but can be extruded), but a cat beam is typically attached to a large amount of ss from the rigging
, galvanized steel
from the anchor
chain and has the potential for electrical
problems from anchor winch wiring
etc. It is a relatively small and light structure compared to these other dissimilar metals.
Despite this it seems common to use this on fiberglass
cats and I cannot see any great additional problems on a wooden structure, but I would look at it carefully.