Aging mechanisms - including general corrosion, pitting/crevice corrosion, galvanic corrosion, microbiologically influenced corrosion, stress corrosion cracking (SCC), creep, fatigue, thermal aging, radiation embrittlement, stress relaxation, and wear - based on literature and operating experience from nuclear and nonnuclear applications.

Naval Nuclear Laboratory has developed Alloy 52i, a high chromium (~27 wt%) weld metal that can be welded onto Alloy 600, Alloy 625, or Alloy 690 wrought material. Alloy 52i by itself has shown to be very resistant to SCC in deaerated pure water. However, there is a concern when welding Alloy 52i onto the more SCC susceptible Alloy 82H or Alloy 600 that the first weld bead would be chromium diluted by the mixing with the lower-chromium base metal. This lower chromium level may lead to higher SCC susceptibility than the surrounding weld metal, since chromium content has shown a correlation with nickel alloy SCC susceptibility. In commercial nuclear power applications, many plant components are limited by SCC propagation in welded components within the weld metal; this test program seeks to understand which weld combinations, with respect to chromium concentration, may yield deleterious SCC properties for improved lifetime of plant components.

The corrosion resistance of sucker rod materials can be a significant concern, especially in aggressive service environments with high acid gas concentrations. Corrosion-related failures have been associated with increased levels of produced hydrogen sulfide (H2S) and carbon dioxide (CO2). The presence of corrosion damage, which is characterized by local material dissolution and pitting formation under the influence of CO2 and/or H2S, provides the initiation sites in a fatigue cracking mechanism. The fatigue crack propagation in corrosion aggressive environments is associated with the following factors: (1) local tensile stress concentration at crack tip, and (2) local corrosion dissolution. Therefore, using a material that tends to re-passivate as it interacts with the environment would be the optimum solution in order to mitigate the likelihood of field failures and reduce overall operating costs. Regarding passive film disruption processes abrasion and high temperature influences were not considered at this stage of the present study and repassivation kinetics were not measured. Conventional sucker rod production processes include normalize and temper (N&T) or quench and temper (Q&T) heat treatments to meet desired strength levels of low alloy steels. In order to enhance the corrosion properties and provide a resistant sucker rod solution, 13Cr martensitic stainless steel may provide a viable alternative to low alloys steels. This paper focuses on the characterization of 13Cr sucker rod material by comparing the general corrosion and corrosion fatigue performance with low-alloy steels.