Azhael wrote
As far as I know, Loricatus can only harden the copper family of metals, up to adamant.
Something to have in mind: Loricatus can come handy even if he doesn't like you. If you are starving you can wield something heavy like a body armor and pray to him, he'll get pissed off and turn your wielded weapon into banana flesh, there you go, free food!
But he might also call up an angel that will turn you into banana flesh.