Plumbing Help - Weeping pipe end

Hi all,

Hope someone out there can help. My boiler has a pipe sticking up out of the top. It is not jointed; it just ends, and is covered in a thin layer of what looks like black waterproofing paint. This is now weeping, enough to cover the flat top of the boiler and drip down. It's not fast but unless I wipe the top of the boiler about 4 times a day, it drips enough for the floor to be wet and soggy.

I have stuck silicone sealer all over this pipe, which has slowed it down but not stopped it. Is there a waterproof paint or something I can buy that will seal the pipe end?

Thanks in advance.