A state trust company may not pledge or create a lien on any of its assets except to secure the repayment of money borrowed or as specifically authorized by RCW 30B.20.010, or by rule, or by a finding of the director that such conduct does not violate any other applicable law and serves the convenience of the state trust company and the public. An act, deed, conveyance, pledge, or contract in violation of this section is void.