corrosion consultancy,corrosion courses,corrosion expert witness

Home | Consulting | Training | Expert Witness | Failure Analysis | Design Review | Corrosion Test | Corrosion Software | Protective Coatings | Materials Selection | Cathodic Protection | >>>

 

Corrosion Modeling Software and Corrosion Prediction Software Series

 CRA-Compass®: Corrosion Modeling and Corrosion Prediction for Corrosion Resistant Alloys

The Threshold Temperature and Chloride Concentration for Pitting, Crevice Corrosion, and SCC   


Version 9.20

 

    Performance        Functionality        Usability

 

Anytime       Anywhere      Any Device      Any OS

No USB dongles     No installation       No Browser Plug-ins


Contact Us for License Details

 

Why WebCorr | Performance Guarantee | Unparalleled Functionality | Unmatched Usability | Any Device Any OS | Free Training & Support | CorrCompass


 

Overview of CRA-Compass

CRA-Compass models and predicts the threshold temperature and chloride concentration for pitting, crevice corrosion, and stress corrosion cracking (SCC) of 60 common corrosion resistant alloys used in water systems including natural seawater, chlorinated seawater, brines, produced water, formation water, brackish water, groundwater, fresh water, and potable water. Users can define their own alloys for CRA-Compass to evaluate the application limits for their resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC) under the specified operating conditions. The performance of the CRAs in coastal/marine atmosphere is also included in this software.

 

Figure 1 below shows the alloy list in the software. Users simply select one of the 60 corrosion resistant alloys from the list or define their own alloy by entering the chemical compositions.

 

Figure 1 Overview of the CRA-Compass

 

After selecting or defining the alloy, the pitting resistance equivalent number, PREN, as defined in the International Standard ISO 15156, is calculated and displayed on the top right corner of the screen.

 

The next step the user needs to do is to select one of the two input parameters, the temperature or the concentration of chloride, both are critical process parameters in many industries. If the user select the temperature as the input parameter (Figure 2), CRA-Compass will determine the threshold temperature or the concentration of chloride for the selected alloy in terms of its resistance to pitting and crevice corrosion for both the plate and weld. The probability of stress corrosion cracking (SCC) and the temperature limit for SCC are also determined. In the application example in Figure 2, for the austenitic stainless steel (AISI Type 347), the PREN is 18 (note that "super"-duplex refers to those with PREN of 40 and above). At the operating temperature of 65°C, the maximum concentration of chloride (for the steel's resistance to pitting and crevice corrosion) is 1,796 ppm and 135 ppm respectively, in non-chlorinated waters and 158 ppm and 12 ppm in chlorinated waters. The open circuit potential, the critical pitting potential, and the repassivation potential are -74 mV, 86 mV, and -357 mV respectively. The probability of chloride stress corrosion cracking is 98.37% when the temperature exceeds 54oC at a chloride concentration of 1,796 ppm in non-chlorinated waters. The SCC crack growth rate after initiation is 40.174 um/day or 14.663 mm/y. The crevice corrosion depth after 4.25 years immersion in seawater is 15.353 µm. The maximum pit depth is 205 µm after 4 years exposure in coastal/marine atmosphere. The surface condition has a rust rating number of 2 based on the Japanese Standard JIS G0595, and this gives a rust surface area ratio of 47%.

 

If the user select the chloride concentration as the input parameter, CRA-Compass will determine the threshold temperature for the selected alloy (Figure 3) in both chlorinated and non-chlorinated waters in terms of its resistance to pitting and crevice corrosion. The probability of stress corrosion cracking (SCC) and the temperature limit for SCC are also determined. If an alloy is susceptible to SCC and the operating temperature is above the threshold temperature, CRA-Compass will predict the crack growth rate of SCC for the selected alloy. The open circuit potential, the critical pitting potential, and the repassivation potential for the selected alloy are computed by CRA-Compass and are displayed under the Output on Threshold Temperature and Chloride Concentration. This predicted values correspond to the measurements in 3.5% NaCl solution at 27°C in the laboratory.

 

Figure 2

   

Figure 3

If an alloy is not in the built-in list, the user can select "User-Defined-Alloy" from the list and then enter the chemical compositions in the table as shown in Figure 4 below. The PREN number and all other predictions are then computed accordingly.

 

 

Figure 4 User-Defined-Alloy

 

Three performance indicators for the selected alloy in the coastal/marine atmosphere are predicted based on the results from 4 years field exposure: (1) the maximum depth of corrosion attack; (2) the form of corrosion (pitting, uniform corrosion, no corrosion); (3) the rust rating number (RN) as per Japanese Standard JIS G0595.

Figures 5a and 5b below show that CRA-Compass models and predict threshold temperature and chloride concentration for both the non-welded plate and the weld of CRAs. 

 

Figure 5a CRA Materials Selection - Comparing the Pitting Resistance of Plate vs Weld

 

 

Figure 5b CRA Materials Selection - Comparing the Crevice Corrosion Resistance of Plate vs Weld 

 

Use of CRA-Compass to Establish Integrity Operating Windows in a Gas Processing Plant

Integrity operating windows are established limits for process variables (parameters) that can affect the integrity of the equipment if the process operation deviates from the established limits for a pre-determined length of time (includes critical, standard and informational IOWs). CRA-Compass is a powerful software tool that can help asset owners and operators quickly and accurately determine the IOW limits. CRA-Compass can be used to determine the temperature and chloride IOW limits for a duplex stainless steel used in a gas processing plant.

 

 

Figure 5c CRA-Compass Software for Determining Integrity Operating Windows (IOWs)

The powerful applications of CRA-Compass are truly unlimited in engineering design, materials selection, process operation, inspection and maintenance, corrosion risk assessment, setting the IOW limits, corrosion modeling and remaining life prediction.

Click here to contact us for licensing details and experience the power of CRA-Compass.


CRA-Compass, giving you the right directions in CRA selection and application.

Home | Contact Us  |  PDF

Copyright © 1995-2021. WebCorr Corrosion Consulting Services. All rights reserved.