A system for field internally coating a pipe joint comprising a polymer application unit, which has a first cart configured to selectively advance inside a pipe; a first and a second tank configured to contain a first and a second polymer component respectively; a mixer to mix the first and the second component; a first and a second pump to feed the first and the second component respectively from the first and the second tank to the mixer; an applicator to apply the polymer to the pipe; and a conduit comprising a free end configured to be placed near the applicator to feed the polymer from the mixer to the applicator.