전기저항 용접강관의 홈부식에 관한 연구

Abstract

홈부식으로 누수사고가 발생한 급수관 시료를 SEM/ECS로 분석하고 황 함유량이 전봉강관의 부식전위와 홈부식 감수성에 미치는 영향에 대하여 연구하였다.

급수용 배관으로 사용한 전기저항 용접강관은 황 함유향이 낮은 경우(55ppm)에는 홈부식이 잘 발생하지 않았으나, 황 함유량이 높은 경(100 ppm 이상)에는 홈부식이 쉽게 발생하여 4년 이내에 홈부식으로 관통되어 누수되는 사례가 관찰되었다.

용접부와 열영향?灌? 결정입도가 미세하여 모재부보다 부식성이 더 높지만 홈부식을 유발하는 근본요인은 아니었고, 전기저항 용접강과능 NaCl수용액(3.5wt.%)에서 황 함유량이 증가함네 따라 부식전위가 감소하였으며 홈부식인자는 증가하였다. 즉 황을 20ppm함유한 강관의 부식전위는 -700mV.SCE이고 홈부식인자는 1.2이며 화을 100ppm 함유한 강의 부식전위는 -750mV.SCE이고 홈부식인자는 1.36이었고 전봉강관 단면부식전위는 표면부식전위보다 약 20mV.SCE 낮은 값을 보였다.

A research for the influence of sulfur content in ERW carbon steel pipe on the corrosion potential and the grooving corrosion sensitivity has been conducted.

ERW carbon steel pipe containing lower sulfur content(55ppm S)used in tap water supply was not easily corroded at the weld line, however, higher sulfur(100ppm) containing pipe was heavily corroded at the weld line locally and leaked within 4 years of water supply.

Corrosion potential and grooving factor depended so strongly on sulfur content that the more fine grains structure of HAZ and weld metal than base metal can not be the main causes of grooving corrosion. The corrosion potential of cross section of pipe was lower about 20mV than that of the surface of pipe.

A research for the influence of sulfur content in ERW carbon steel pipe on the corrosion potential and the grooving corrosion sensitivity has been conducted.

ERW carbon steel pipe containing lower sulfur content(55ppm S)used in tap water supply was not easily corroded at the weld line, however, higher sulfur(100ppm) containing pipe was heavily corroded at the weld line locally and leaked within 4 years of water supply.

Corrosion potential and grooving factor depended so strongly on sulfur content that the more fine grains structure of HAZ and weld metal than base metal can not be the main causes of grooving corrosion. The corrosion potential of cross section of pipe was lower about 20mV than that of the surface of pipe.