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CRA-Compass®: Your Guide to Corrosion Resistant Alloys - Corrosion Prediction, Selection and Application Limits for Resistance to Pitting, Crevice Corrosion and SCC  


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Features and Component Modules of CRA-Compass

CRA-Compass consists of the following standalone modules:

CRA-Compass for Waters and Brines

CRA-Compass for Acids and Alkalis (H2SO4, HNO3, H3PO4, HCl, HF, Acetic Acid, Formic Acid, NaOH):

  • CRA-Compass-H2SO4: sulphuric acid corrosion predictor for corrosion resistant alloys, with iso-corrosion charts in sulphuric acids.

  • CRA-Compass-HNO3: nitric acid corrosion predictor for corrosion resistant alloys, with iso-corrosion curves in nitric acids.

  • CRA-Compass-H3PO4: phosphoric acid corrosion predictor for corrosion resistant alloys, with iso-corrosion diagrams in phosphoric acids.

  • CRA-Compass-HCl: hydrochloric acid corrosion predictor for corrosion resistant alloys, with iso-corrosion charts in hydrochloric acids.

  • CRA-Compass-HF: hydrofluoric acid corrosion predictor for corrosion resistant alloys, with iso-corrosion curves in hydrofluoric acids.

  • CRA-Compass-CH3COOH: acetic acid corrosion predictor for corrosion resistant alloys, with iso-corrosion diagrams in acetic acids.

  • CRA-Compass-HCOOH: formic acid corrosion predictor for corrosion resistant alloys, with iso-corrosion charts in formic acids.

  • CRA-Compass-NaOH: sodium hydroxide corrosion predictor for corrosion resistant alloys, with iso-corrosion curves in sodium hydroxide.

Overview of CRA-Compass for Waters and Brines

 

This module deals with the application limits of 55 common corrosion resistant alloys used in water systems including natural seawater, chlorinated seawater, brines, brackish water, groundwater, fresh water, and potable water. Users can define their own alloys for CRA-Compass to evaluate the application limits for the resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC). The performance of the CRAs in coastal/marine environment is also included in this module.

 

Figure 1 below shows the overview of the CRA-Compass for waters. The user simply selects one of the 55 alloys from the list or define his/her own alloy by entering the chemical compositions.

Figure 1 Overview of the CRA-Compass for Waters

 

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

 

The next step the user needs to do is to select one of the two input parameters, the temperature or the concentration of chloride. If the user select the temperature as the input parameter (Figure 2), CRA-Compass will determine the application limit or the maximum concentration of chloride for the selected alloy 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 the user select the chloride concentration as the input parameter, CRA-Compass will determine the application limit or the maximum 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. The critical pitting potential, Epit, for the selected alloy is computed by CRA-Compass and is displayed under the Output on Application Limit. This predicted value corresponds to the measurement in 3.5% NaCl solution at 30oC 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 degradation rating number (RN) as per JIS G0595.

 

Overview of CRA-Compass for Acids and Alkalis (H2SO4, HNO3, H3PO4, HCl, HF, Acetic Acid, Formic Acid, NaOH)

 

Figure 5 below demonstrates the operation of CRA-Compass for Acids and Alkalis, which is similar to the operation of the CRA-Compass for Waters discussed above. The user simply select an alloy from the dropdown list, and then enter the temperature and concentration. CRA-Compass for Acids will determine the boiling point of the acid, and the predicted corrosion rate of the selected alloy at the specified temperature and concentration. In addition to that, CRA-Compass for acids will compute the iso-corrosion diagram for the selected alloy so as to give the user a complete picture of the corrosion behavior of the selected alloy across the entire range of acid concentration and temperature.

Figure 5 CRA-Compass for Acids and Alkalis

 

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

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