Stress Corrosion Cracking (SCC) is a sudden and difficult-to-predict severe degradation mode of failure of nuclear, petrochemical, and other industries. This is a development proposal for a methodological software based in: the propensity of SCC failure plus a kinetic model link which better describes the failure evolution. The main result is to predict failures with an adequate statistical regression.

1) A fixed combination of material-environmental condition is plotted on a potential-pH (Pourbaix) diagram marked with corrosion submodes – which can be originated from literature and/or experimental data [1]. This forms a Knowledge Base (KB) for SCC-Propensity. Fuzzy Logic can be used to determine the SCC-Propensity zones.

2) When the actual corrosion submode of the concerning material-environment is marked, based on new experiments, a feedback should be sent to the KB.

3) Over the determined point (or region) in a SCC submode, a proper kinetic model should be choose (departing for example from a kinetic library model-KB) to adjust the experimental data from the concerning material-environment.

4) The regression quality of the model adjusted should be proper statistically evaluated, and a feedback should be
“fuzzylogically” retrofit its adequacy.

There are already various isolated existing programs which can be combined to build this methodological software. So, for example, in phase 1) it can be used Thermo-Calc for computational thermodynamics, and Pourbaix Diagram construction. In phase 3) there are also various SCC-kinetic models programs like the Film Rupture of Ford Andresen (General Electric Property), the Coupled Environment Fracture Model (CEFM) of Digby D. Macdonald, and others [2]. The general concept is resumed in Figure 1. Some pre-evaluation essays based in this methodology, using experimental tests done in Brazil, were essayed in our DSc. Thesis - in Portuguese, but resumed in reference [3].

The main potential benefit is to offer a practical software to solve immediate necessity to prevent SCC for industries.
The main idea of this product is from Staehle [1], but despite its brilliancy, it seems never applied to build an engineering tool.

The investment cost can be also reduced because there are various existing programs, and the main cost maybe must be to obtain the proprietary licenses of these ones.

References:

[1]. R.W. Staehle, Combining design and corrosion for predicting life, in: R.N. Parkins (Ed.),Life Prediction of Corrodible Structures, vol. 1, NACE International, Houston, 1994, pp.138-291.

[2]. R.B. Rebak, Z. Szklarska-Smialowska, The mechanism of stress corrosion cracking of alloy 600 in high temperature water, Corros. Sci. 38 (1996) 971-988.

[3]. O.F. Aly; A.H.P. Andrade; M. Mattar Neto; M.M.A.M. Schvartzman. Results On Modeling of Primary Water Stress Corrosion Cracking at Control Rod Drive Mechanism Nozzles of Pressurized Water Reactors. In: 19th International Conference on Structural Mechanics in Reactor Technology, 2007, Toronto. SMiRT 19 Transactions. Raleigh, NC, USA, 2007. pp. 1-8.