Among the several threats to bolting in marine environments, hydrogen embrittlement is one of the most dreaded. A form of environmentally assisted cracking (EAC), hydrogen embrittlement occurs when hydrogen penetrates a fastener’s base material, making it fragile and more susceptible to failure. This paper addresses the severity of marine environments and how different metallic coatings influence the amount of hydrogen present in carbon steel bolting. From laboratory generated data, environmental severity and risk of hydrogen embrittlement are estimated and correlated to actual field performance from the literature. This investigation relates the interplay of environment, stress, and material.
The metallic coatings evaluated in this investigation are Zinc, Zinc-Nickel, and ASTM B994 Nickel-Cobalt plating. Zinc and Zinc-Nickel are common coatings currently used in both critical and non-critical bolting in the oil and gas industry. ASTM B994 Nickel-Cobalt is a novel material with many offshore applications, including highly-critical subsea environments.