Any city which desires to issue bonds as provided by Sections 11-81-22 through 11-81-24 to refund the principal of any of its unmatured bonds may establish a sinking fund which shall be used solely for the purposes of paying the principal of such unmatured bonds and may, by resolution adopted by its city council or board of commissioners or other governing body, employ any bank or trust company authorized to do business in the State of Alabama or any savings and loan association organized either under the laws of the State of Alabama or of the United States to act as trustee of such sinking fund and to hold in trust the bonds of such city issued to refund the principal of such unmatured bonds and placed in such sinking fund and to apply the income therefrom and the money received in payment therefor or any other income which shall accrue to such sinking fund to the payment of the principal of such unmatured bonds.