What is the black stuff on black iron pipe

[Roger Feeley]

I got some today to make some additional ladder rungs for a playset. When I did the first batch, I degreased with mineral spirits and then painted and it was still kind of hard to paint. Today, I chucked up the pipes in the wood lathe and sanded most of the paint off. The paint still didn't go on all that smoothly.

So what is that stuff? some sort of creosote or other toxic waste?

[Greg Parrish]

Don't know what it is but it is hard to paint. I’ve had some luck for furniture leg bases with cleaning with mineral spirits numerous times, light sanding and spray on primer. Then painting with top coat.



I got some today to make some additional ladder rungs for a playset. When I did the first batch, I degreased with mineral spirits and then painted and it was still kind of hard to paint. Today, I chucked up the pipes in the wood lathe and sanded most of the paint off. The paint still didn't go on all that smoothly.

So what is that stuff? some sort of creosote or other toxic waste?

[Frank Pratt]

Seems like it's almost a cross between wax & paint. Nasty stuff to remove though.

[Roger Feeley]

Seems like it's almost a cross between wax & paint. Nasty stuff to remove though.
It was. I would say that I got it down to 80% bare metal.

[Larry Frank]

I believe it is bituminous asphalt and yes difficult to remove.

[Bill Dufour]

Also known as tar. I bet a blowtorch would burn it off.

[Ole Anderson]

Google can be your friend: https://www.google.com/search?q=what+is+the+coating+on+black+iron+pipe&oq=what+is+the+coating+on+black+iron+pipe&aqs=chrome..69i57j0.10742j0j7&sourceid=chrome&ie=UTF-8

One of the posts says it is a varnish/asphalt type coating and MEK is the best solvent for removing it.

[Dave Cav]

It could also be coal tar pitch, especially if the pipe is from an offshore source that isn't too particular about toxic waste issues. If it IS CTP, then there isn't much other than a torch or friction that will take it off. Coal tar pitch used to be pretty common in the hot roofing industry, and it lasted a long time because of it's cold flow properties. When I was in the roof consulting business our test for regular petroleum asphalt vs coal tar pitch was to put a small sample in a vial of WD-40 and let if sit for a day or two. If it started to dissolve it was petro. If it just sat there it was coal tar.