Field Kelvin Probe: progress made towards rapid, in-situ evaluation of HISC susceptibility and undercoating corrosion

摘要

Unambiguous detection of corrosion long before typical corrosion signs are discernible or detectable by current inspection technologies is important for the offshore oil and gas industry as with offshore operations minor defects can develop quickly into major failures. The Field Kelvin Probe (FKP) is an emerging inspection technology aimed at detection of corrosion onset. Based on a capacitive sensor, the FKP is a contactless technology capable of measuring absolute corrosion potentials and diffusible hydrogen concentrations in steel. Our work on realistic test panels proves that FKP detects incipient corrosion even if obscured by industrial grade coatings. FKP data was compared with the results achieved with a Scanning Kelvin Probe (SKP) on identical samples. Apparently, electrostatic charge trapped by the coating impedes the measurements. Solutions to mitigate charge effects and to enable the undercoating corrosion detection are discussed. An SKP fitted with an electrochemical cell was used for real-time monitoring of hydrogen permeation through low-carbon and alloyed steel coupons. Parallel FKP testing provided strong evidence that hydrogen detection is doable with a portable FKP on offshore installations. These findings and the preliminary data obtained with an FKP sensor designed for subsea use reinforces the belief that FKP-aided detection of early corrosion and hydrogen concentration on submerged installations could serve as an indicator of hydrogen embrittlement risk.