Potential New Applications of SQUIDS and SQUID Arrays in NDE

SQUIDs: microscopes and nondestructive evaluation

“…Among the first experiments on SQUID NDE were the remote detection of surface breaking cracks in ferromagnetic steel by Bain et al [19], plastic deformation in magnetic steels by Evanson et al [20], Barkhausen jumps in iron samples by Weinstock et al [21] and the location of metal pipelines by Weinstock et al [22]. In other work, Bellingham et al [23] studied electrolytic corrosion processes in non-voltaic cells, and Hibbs et al [24] measured corrosion currents with a SQUID array. Wunderlich et al [25] studied the field gradient distribution of hardened steel cylinders with a HTS SQUID to detect mechanical stress in such cylinders.…”

Scanning Squid Microscopy

“…Several years ago, a group at MIT demonstrated that SQUIDs could be used to measure corrosion noise in a zinc sample immersed in concentrated hydrochloric acid (67-70), but these studies effectively utilized the SQUID as a low-impedance, low-noise ammeter incorporated into a conventional electrochemical measurement system and did not, in fact, explore the ability of SQUIDs to make measurements that would otherwise be impossible with conventional techniques. Hibbs et al have shown that SQUIDs can detect filiform corrosion underneath the paint covering aircraft aluminum and can map the corrosion in a simulated lap joint exposed to concentrated sodium hydroxide and have pointed out that the observed magnetic fields were significantly smaller than would be expected from Faradaic considerations alone (71)(72)(73). Recently, a German group has shown that a high-temperature superconductivity SQUID can be used to detect corrosion in aluminum aircraft components (74).…”