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Prep process for adding proseal on existing proseal

RVFan671

Well Known Member
I'm doing the desloshing in my RV-4 and here and there a chunk of the proseal that was over a rivet on a rib is lifing and pulling off. I dont think the inside of the rib where the shop head is located was scuffed (not sure if plans call for it even).

Looking for advice from those who have fixed leaks in tanks or know what the standard procedure is for adding more proseal. I'm cleaning the slosh out with MEK so I plan to use it to clean before applying any proseal but I'm not sure if I need to scuff any existing proseal or not and if so, with what (grit sandpaper or scotchbright).
 
What I do

My day job is overseeing the depot maintenance on KC10 tankers..Proseal by the gallons. I also built my -4(No leaks in 15 years), and have successfully re-sealed other "leakers". My personal preference, as well as standard operating procedure for re-coat is to remove loose and contaminated sealant to the best of ability.Clean the surface with Coleman lantern fuel or Naptha, Then scuff the surrounding area of bare metal, existing sealant and faster heads with Scotchbright (I use red pads) to promote adhesion, clean again with Coleman lantern or Naptha (Coleman fuel is my all time go-to for residue free results) Apply sealant with Acid brush or similar to cover all areas. Save a blob on a dated card for cure test. Most sealant used for tanks is the "B" consistency, which is thick and a little stubborn to apply, but perfect for building/joining parts. I use "A" which is brushable and flows into nooks and crannies when topcoating, although "B" can be thinned slightly with MEK to a similar consistency...I actually enjoy working with Proseal, and it needs to be accomplished with artistic like finesse to be done correctly..have fun!
 
Thanks for the input. I'll be following the guidance and will be posting a thread about my desloshing experience in Hope's it helps someone else down the road too.
 
I would not recommend thinning "B" type Proseal with MEK.

It has not been proven conclusively, but one of the primary hypotheses for the tank rivet blister problem on QB tanks from the shop in the Phillipines is that they were thinning the Proseal with MEK. It seems to permit fuel vapor (not liquid) to percolate through it.

Using the "A" stuff for re-coat is good advise.
 
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