When the hot wax fails to eradicate my slave's unauthorized erection, I decide that he'll now be to stay hard even during an excruciatingly painful vampire glove handjob!
Each time his cock starts to get soft from the pain of the sharp metal spikes shredding his dick, I it into the cock pump until its nice and hard again before taking it out and wrapping my steel barbed hands around his aching cock again.
After this, he'll definitely take his chastity seriously.