[DSM8]

while working on my latest project I was enclosing lengths of tube with hemispherical ends (there were holes in each end so blowout was not an issue).
Several of the hemisphere's had rust on the inside at the joint. I sanded them clean to shiny metal but was trying to think of something I could do to the inside either pre or post weld that would allow me some degree of rust prevention etc so it would not be an issue down the road sometime.

Any thoughts?

Example of what I am working with.

[weldin mike 27]

Are the holes going to remain? I reckon, slight warming up in an oven, some sort of moisture dispersent (metho or something) then a clear lacquer spray using a straw of some kind to get some inside.

[DSM8]

Are the holes going to remain? I reckon, slight warming up in an oven, some sort of moisture dispersent (metho or something) then a clear lacquer spray using a straw of some kind to get some inside.

Yes the holes will remain, I was thinking along the same lines. Ideally it would be nice if i could apply a weld through primer on the back side but I dont know how that would work with the tig.

[weldin mike 27]

You could paint the the inside but I think weld through primers are a bit of a pipe dream. As you said, tig hates everything. Could paint bits of the inside, away from the weld zone, then do what we said after.

[DSM8]

Coasting the inside of the finished product with lacquer seems to be the easiest approach. I can thin it out some and then pour it in one end and swirl it around to coat the inside.

Just a preventive step on my side.

Thought would ask to see if there was another method used by the masses, I am good to go with this one.

[weldin mike 27]

Easiest way.

[Otto Nobedder]

The holes remain permanently open to atmosphere?

Dump 8 oz. of clean dry sand (like blasting sand... think garnet or Black Beauty) in, duck-tape it shut, and put it on a paint shaker for ten minutes.

Then, dump, rinse, dry. Add the coating of your choice (laquer is good, epoxy is better), tape it back up, and put it back on the shaker.

Two cents from someone who has "all of the above" at his disposal.

Steve S

[motox]

im not sure what you are using these for but
there are coatings that are used to seal old
motocycle gas tanks avalable that are poured
in and swished around. when used they recommend
putting a handful of nuts or washers and shaking it
around to remove loose scale. i like steve's idea better.
its been a while since i used any but i think the brand
name is Kreem.
craig