Crevice corrosion temperature

Table 4.43 Critical pitting and crevice corrosion temperature per ASTM G-48...

Crevice corrosion is, of course, dependent on temperature. No crevice corrosion is found to occur below a certain temperature called the critical crevice corrosion temperature, which is similar to the critical pitting temperature mentioned earlier. The critical crevice corrosion temperature has been used as a measure to evaluate metallic materials for the susceptibility to crevice corrosion [63],... 

The steel that is ranked highest in relation to pitting and creviee eorrosion in Table 10.7 is also represented in Figure 10.4 (20-25-4.5, i.e., 20Cr25Ni4.5Mo). The figure shows that the newer austenitic steels 20-18-6 and 24-22-7 as well as the ferritic-austenitic steel 25-7-4 are even better. The eolunms in the figure indieate critieal pitting temperature and critieal crevice corrosion temperature for rolled products as tested in a 6% FeCU solution. 

Figure 10.4 Critical pitting temperature (CPT) and critical crevice corrosion temperature (CCT) for various stainless steels in 6% FeCb solution [10.9]. The figures below the columns show the contents of Cr, Ni and Mo, respectively (compare Tables 10.5 and 10.6).

CCT Critical crevice corrosion temperature HAZ Heat-affected zone... 

To overcome these limitations. Method D measures the critical crevice corrosion temperature, using a multiple crevice assembly (MCA). The test solution is 6 wt. percent FeCl3 acidified with 1 wt. percent HCl. This test method is also referenced in ASTM G 157 for evaluating the corrosion properties of wrought iron- and nickel-based corrosion resistant alloys for the chemical process industries. 

AHoy/Laboratoiy Method C—CPT Critical Pitting Corrosion Temperature (C) Method D—CCT Critical Crevice Corrosion Temperature (C) ... 

The materials Monit and Sea-Cure are characterised by good resistance to pitting, crevice and stress corrosion cracking in seawater. The critical pitting corrosion temperature in the FeCls test is 328 K (55 °C) and the critical crevice corrosion temperature is 318 K (45 °C). In Table 36, the pitting potentials of the two superferrites and the austenitic steels 1.4539 (SAE 904 L, XlNiCrMoCu25-20-5) and X3CrNiMol7-13-3 (SAE 316,1.4436) measured in 5% NaCl solution are presented. 

In the iron(III) chloride test, these nitrogen-alloyed steels show higher values for the critical pitting and crevice corrosion temperatures than comparably alloyed nitrogen-free steels [130]. 

Steel Pitting corrosion temperature. Crevice corrosion temperature,... 

Table 41 Critical pitting and crevice corrosion temperatures in the FeCl3 test of 1.4404, 1.4539 and 1.4547 [1 76]...

These materials are passive in seawater and, up to temperatures of 333 K (60 °C), practically resistant to uniform surface corrosion. The resistance to pitting and crevice corrosion and the critical pitting and crevice corrosion temperatures are determined mainly by the content levels of chromium and molybdenum and therefore increase with the pitting resistance equivalent. The materials listed in the Table are resistant to stress corrosion cracking in seawater, even at higher temperatures, and less sensitive to corrosion fatigue. They are also suitable for use at higher flow rates up to about 20 m/s [23]. 

The critical crevice corrosion temperature of an alloy is the temperature at which crevice corrosion is first observed when immersed in a ferric chloride solution. Table 1.3 lists the critical crevice corrosion temperature of several alloys in 10% ferric chloride solution. 

Alloy Pitting Temperature, °C F Crevice-Corrosion Temperature, °C °F ... 

Critical Crevice Corrosion Temperature for the Duplex and some Austenitic Stainless Steels In 101 FeCl3-6H20 (pHl) ... 

Comparative Immersion Pitting and Crevice-Corrosion Temperatures in Oxidizing NaCI-HCI Solution... 

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