Science-Based Mapping of Stress Corrosion Cracking Thresholds for Stainless Steel

  • Farhat, Hanan Alshareef (Lead Principal Investigator)
  • da Silva de Sa, Jonas (Post Doctoral Fellow)
  • Haboub, Amine (Research Associate)
  • Fellow-2, Post Doctoral (Post Doctoral Fellow)
  • Assistant-1, Research (Research Assistant)
  • Ramesh, Dr.Abitha (Principal Investigator)
  • Laycock, Dr.Nicholas (Consultant)
  • ghosh, Dr.sukanta (Principal Investigator)
  • Sundararajan, Mr.Guruprasad (Principal Investigator)
  • Newman, Prof.Roger (Principal Investigator)

Project: Applied Research

Project Details

Abstract

Within the Oil & Gas industry, metals represent around 60% of total industry spending [1]. Unfortunately, those metals are potentially susceptible to corrosion, which is estimated to cost about 3% of global GDP and nearly $8 billion p.a. in Qatar. Corrosion-related equipment failures also carry the potential for loss of human lives and significant harm to the environment. Consequently, there is a strong driver to eliminate these risks by selection of more corrosion resistant materials. At the same time, the environments in which materials must perform are becoming ever more aggressive [2-4] and industry expenditure on special alloy steels, stainless steels and nickel-base alloys has grown substantially [2]. In this project, we propose to address one specific and potentially catastrophic failure mechanism: chloride-induced Stress Corrosion Cracking (SCC) of austenitic stainless steels. This form of cracking can occur at high rates and at low stress levels and is hence a critical consideration in the design and safe operation of many industrial facilities. However, in some applications where very high chloride concentrations may be present, the current industry approach is inherently conservative, often leading to the selection of very expensive nickel-base alloys. Several different electrochemical conditions have been identified as capable of initiating chloride SCC, from localized corrosion sites in otherwise passive surfaces, to uniform corrosion in acidic chlorides, to semi-passive states in very high chloride solutions. The last is the least well understood at the moment, and is challenging to study, for reasons mentioned later. In this work, we aim to unify these conditions within one mechanistic framework, which will then be used to develop multi-dimensional ‘maps’ of safe-use boundaries for common (relatively inexpensive) stainless steels in terms of the identified critical factors. Although it may sound simple, the proposed objective has never been achieved and ranks as a huge gap in industrial materials selection capability. The experimental program will be divided into four interacting Work Packages. The base environments will be Ammonium Chloride (NH4Cl) and Magnesium Chloride (MgCl2) solutions of varied concentrations. Advanced electrolyte modeling, based on OLI Systems technology [6-8] and related literature, will be used to obtain (and where possible verify) predictions of important SCC parameters like pH. SCC testing will be carried out at Qatar Environment and Energy Research Institute (QEERI) and Shell as a function of relevant parameters (salt concentration, temperature, pH), primarily in controlled-potential tests using samples of Type 316L stainless steel. Shell will specialize in MgCl2 solutions, and QEERI in NH4Cl solutions. Such an approach requires a subtle understanding of the relationship between the electrode potential, imposed in such tests, and the oxygen concentration in practice, as well as the possible effects of other impurities – this will be the major part of the activity at University of Toronto (UT). Regarding the impurities, conventionally sourced salts will show a big difference in purity between NH4Cl (made by reacting HCl and NH3, and thus nominally free of heavy metals) and MgCl2 (commonly prepared from seawater or other salt sources). Advanced facilities such as TOF-SIMS are available in UT for impurity analysis. The fourth and final Work Package concerns the development of science-based maps for SCC thresholds, their incorporation into an industrially useful format and their dissemination to the wider industry. This part of the work will be led by Materials & Corrosion Engineers at Shell and will draw on the Data Science and Data Visualization resources within the extensive Computational Science team at Qatar Shell Research and Technology Centre – Shell Technology Centre Bangalore (Shell). At this stage we envisage potential commercialization of the technology through licensed software, as has been successful previously for other technologies developed by Shell, including corrosion prediction programs such as Hydrocor [3] and ASSET [10,11], and the S-RBI Risk Based Inspection system [4].

Submitting Institute Name

Hamad Bin Khalifa University (HBKU)
Sponsor's Award NumberNPRP13S-0205-200268
Proposal IDEX-QNRF-NPRPS-19
StatusActive
Effective start/end date15/06/2115/12/24

Collaborative partners

Primary Theme

  • None

Primary Subtheme

  • None

Secondary Theme

  • None

Secondary Subtheme

  • None

Keywords

  • Corrosion,Corrosion engineering,Material science,Corrosion and electrochemistry,Corrosion damage
  • None

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