地下水と川水の混合水によるアルミニウム黄銅管の応力腐食割れ

抄録

Aluminum brass pipes in the cooler for transformer oil have been suffered from corrosion cracking at the Numazawanuma Power Station for recent several years. Underground water and the Tadami River water are alternately used as cooling water. The static stress-corrosion test on aluminum brass pipes were carried out using underground water, cooling water for transformer oil and the Tadami River water at the Numazawanuma Power Station. The following conclusions were obtained from the results of the test.
(1) The cracking of aluminum brass pipes in the cooler is due to stress-corrosion in cooling water.
(2) The stress in stress-corrosion cracking is originated by fixing process of pipes in the cooler.
(3) A corrosive substance in cooling water may be sulfur.
(4) Stress-corrosion cracking of aluminum brass pipes in the cooler will occure at an applied stress of 2kg/mm² in two years.
(5) Aluminum brass pipes were suffered from general corrosion by underground water, but they were almost in passive state in river water. Stress-corrosion cracking were scarcely occurred in either underground or river water. Nevertheless, stress-corrosion cracking were easily occurred in cooling water that consists of underground and river water.
(6) The form of cracks in aluminum brass pipes is perfectly identical in both case of practical use and experiment. All cracks start from pitting and they are transcrystalline.