§ 34. Exemption of materials or equipment from execution. All materials or equipment furnished or partly procured on a defaulted contract with the corporation, shall be exempt from execution, but the corporation shall pay the moneys due for such material or equipment to any judgment creditor of the contractor under whose execution such materials or equipment might otherwise have been sold, on production to it of due proof that such execution would have so attached, and such payments shall be valid payments on the contract.