do you mean where the aluminum tube is set on the carbon/glass black rudder stock? If it is anything like mine then it appears to be glued/epoxied and then riveted to it. is this what you are talking about?
or are you talking about the fitting that attaches the tiller to the crossbar? if this is the case it shouldn't be corroded cause it is plastic to alumimum (if, once again, it is like mine with the black plastic fittings that have the pin that is secured with the little clip). one of mine pulled out last time I went over. easy fix with a new screw and some jbweld (have to be careful not to have the screw go into the threaded part though. the diameter is slightly different and I used al strips from a can to make a "spacer")