i cut and past this from a reply i did on FB yesterday ..looks like good electrical tape applied well can last 35 years.. i never had any problems with any joint i have ever done unless there was a mechanical fail
>>>>to seal joints i use just good quality electrical tape..i make certain i keep it tight and slightly stretched when rapping it ..i have remains of a 5/8th wave i made when i was 18 laid down outside at the back of a shed on the floor and all the roof water falls on it as no gutter..the other year i was short of a jubilee clip and remembered the old antenna i cut the tape and the clip was relatively rust free would have been second hand as all the ally on the antenna was and the joint was pretty good with any corrosion looking like moister had got in from the inside of the antenna..probably as lade on its side ..it was probably about 35 years old .... i have not had as good look with self-amalgamating tape i used quality 3M self-amalgamating tape on my Sirio V4K ,, I take it down to repair the basket after about 18 months i find that the tape had stuck to its self very well but not so well to the aluminum exspaily around tight radiuses and their was sighns of water ingres and slight corrishion under it ,, i remuved it all and relaced it with good quality electrcal tape......... bugger the spell cheker has stoped