Iowa Code § 491.59

In none of the cases contemplated in this chapter can the private property of the stockholders be levied upon for the payment of corporate debts while corporate property can be found with which to satisfy the same; but it will be sufficient proof that no property can be found, if an execution has issued on a judgment against the corporation, and a demand has been thereon made of some one of the last acting officers of the body for property on which to levy, and the officer neglects to point out any such property.