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What is this black stuff around my tank access cover?

RVFan671

Well Known Member
I'm desloshing my '91 RV-4 tanks and the access covers had cork gaskets. I plan to seal the cover plate with proseal only.

I'm wondering what the black stuff is on the outside edge of the doubler for the cover plate? It is soft. Is it old proseal that broke down or something else? Should I try and remove it and put a ring of proseal around the outside edge of the doubler ring?
 

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I'm desloshing my '91 RV-4 tanks and the access covers had cork gaskets. I plan to seal the cover plate with proseal only.

I'm wondering what the black stuff is on the outside edge of the doubler for the cover plate? It is soft. Is it old proseal that broke down or something else? Should I try and remove it and put a ring of proseal around the outside edge of the doubler ring?

Looks like old proseal to me.

I agree. Looking at the photos makes me think it is old polysulfide. (ProSeal (TM) or one of the other commercially available tank sealants.)
 
Given that it is soft and I'm going to be laying down some new proseal elsewhere in the tank, should I try to clean up the soft stuff, scuff and add a fillet on the perimeter of that cover plate backer?
 
Given that it is soft and I'm going to be laying down some new proseal elsewhere in the tank, should I try to clean up the soft stuff, scuff and add a fillet on the perimeter of that cover plate backer?

Yeah, as much work as it might be, now is the time to get it squeaky clean - then you always know what you’re starting with, and the new Pro-Seal will do a good job on the access cover.
 
Definitely go the extra mile to remove as much of the soft stuff as you can. I didn't when I re-did my access cover seals, and now I have to pull the tanks again and do it because the soft stuff is leaking. :(
 
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