611.15  Judgments annulled in equity.
  Judgment obtained in an action by ordinary proceedings shall not be annulled or modified by any order in an action by equitable proceedings, except for a defense which has arisen or been discovered since the judgment was rendered. But such judgment does not prevent the recovery of any claim, though such claim might have been used by way of counterclaim in the action on which the judgment was recovered.
[R60, §2621; C73, §2522; C97, §3440; C24, 27, 31, 35, 39, §10952; C46, 50, 54, 58, 62, 66, 71, 73, 75, 77, 79, 81, §611.15]
See 
R.C.P. 1.241