All moneys derived from the sale of any revenue bonds issued under the provision of this article shall be used solely for the purpose or purposes for which the same are authorized, including any engineering, legal and other expenses incident thereto, and, in the case of bonds issued in whole or in part for construction, interest on such bonds or such part prior to and during construction and for one year after completion of construction and, in the case of bonds issued for the purpose of refunding outstanding revenue bonds, any premium which it may be necessary to pay to redeem or retire such bonds. If the proceeds of the bonds of any issue shall exceed the amount required for the purpose or purposes for which the same are issued, the surplus shall be paid into the fund provided in Section 11-81-181 for the payment of the principal of and interest on such bonds.