Sanicro® 28 is a high-alloy multi-purpose austenitic stainless steel for service in highly corrosive conditions. The grade is characterized by: — Very high corrosion resistance in strong acids — Very good resistance to stress corrosion cracking (SCC) and intergranular corrosion in various environments — High resistance to pitting and crevice corrosion — Good weldability Product standards Seamless tube and pipe: ASTM B 668, EN 10216-5, SEW 400 (Feb 1991), SS 14 25 Plate, sheet and strip: ASTM B 709, EN 10088-2, SS 14 25 84 Fittings: ASTM A 403 (chemical composition and mechanical properties according to ASTM B668) Approvals - Approved by the American Society of Mechanical Engineers (ASME) for use in accordance with ASME Boiler and Pressure Vessel Code, section III, section I (Code Case 1325-18) and section VIII, division 1. Datasheet last updated 5/9/2025 6:38:20 AM (supersedes all previous editions)

— VdTOV-Werkstoffblatt 483 (Austenitischer Walz- und Schmiedestahl) — NACE MR 0103 (Materials Resistant to Sulfide Stress Cracking in Corrosive Petroleum Refining Environments) — NACE MR0175/ISO 15156 (sulfide stress cracking resistant material for oil field equipment) Chemical composition (nominal) % Due to its outstanding corrosion properties, Sanicro® 28 can be used in the most diverse environments. Listed below are a few examples of applications for which this alloy is particularly suitable. Today, Sanicro® 28 is the most widely used metallic material for evaporator tubes in the manufacture...

corrosion. The performance of Sanicro® 28 has been excellent. In seawater-cooled heat exchangers and heat exchangers that work with chloride-bearing cooling water, Sanicro® 28 offers high corrosion resistance to both the water and the cooled medium. When a seawater-cooled plant is shut down, there is no need to drain the piping system or flush with fresh water, provided that the shutdown period is shorter than one month and the water temperature is lower than 30°C (85°F). The duplex stainless steel SAF™ 2507 is more resistant than Sanicro® 28 in sea water. Sanicro® 28 was originally developed...

Corrosion rate, mm/year (mpy) Cl , ppm Figure 1. Corrosion rate in contaminated phosphoric acid at different chloride concentrations 100°C (210°F). Comparison of Sanicro® 28 and other alloys (chemical compositions given in table 1). Datasheet last updated 5/9/2025 6:38:20 AM (supersedes all previous editions)

Corrosion rate, mm/year (mpy) Figure 2. Corrosion rate in contaminated phosphoric acid at different temperatures for Sanicro® 28 and some other alloys (chemical compositions given in table 1). Figure 3 is an isocorrosion diagram for Sanicro® 28, Alloy 904L and ASTM 316L in deaerated sulfuric acid. As can be seen from the figure, Sanicro® 28 is more resistant than the other alloys. Naturally aerated sulfuric acid is more corrosive than deaerated acid in the intermediate concentration range. Sanicro® 28 exhibits very good corrosion resistance in concentrated acid. Figure 3. Isocorrosion diagram...

represent a corrosion rate of 0.1 mm/year (4 mpy). Sulfuric acid is sometimes contaminated with chlorides which increases the corrosivity of the solution. However, Sanicro® 28 has good resistance, better than 904L, also in chloride contaminated sulfuric acid, especially at high concentrations. Above about 20% sulfuric acid Sanicro® 28 is even more resistant than the super-duplex stainless steel SAF™ 2507, see isocorrosion diagram in figure 4. Figure 4. Isocorrosion diagram for Sanicro® 28 in sulfuric acid containing 2000 ppm chloride ions at a corrosion rate of 0.1 mm/year (4 mpy). Sanicro® 28...

increases when chlorides are present. Table 2 and 3 demonstrate the good resistance of Sanicro® 28 against general corrosion and SCC in sodium hydroxide contaminated with chlorides. Table 2. SCC in boiling 43% NaOH + 6.7% NaCl, 142°C (288°F), Sanicro® 28 Alloy 800 Alloy 904L Table 3. General corrosion in NaOH and in NaOH+NaCl, mm/ year. NaOH NaOH+ As can be seen, Sanicro® 28 is superior to both Alloy 800 and Alloy 904L. Datasheet last updated 5/9/2025 6:38:20 AM (supersedes all previous editions)

Corrosion rate, mm/year <mpy) Figure 6. Corrosion rates in hydrofluoric acid at 20°C (68°F) for Sanicro® 28, Alloy 904L and AISI 316. Datasheet last updated 5/9/2025 6:38:20 AM (supersedes all previous editions)

HCOOHr wdght-% Figure 7. Isocorrosion diagram for Sanicro® 28 and other alloys in formic acid at a corrosion rate of 0.1 mm/year (4 mpy). Sanicro® 28 can withstand very high temperatures in aggressive environments without being attacked by pitting. Figure 8 shows the critical pitting temperature (CPT) for some alloys in chloride-bearing water with a salinity comparable to that of sea water. The figure shows that Sanicro® 28 has a higher critical pitting temperature (CPT) than Alloy 904L and Alloy 825 even in acidic chloride solutions. The curves are displaced at higher temperatures in solutions...

joints. For further information, see Alleima R&D lecture S-58-7-ENG. Figure 8. Critical pitting temperature (CPT) at +400 mV SCE for different alloys in synthetic seawater (3% NaCl), at different pH values (chemical compositions give in table 1). Datasheet last updated 5/9/2025 6:38:20 AM (supersedes all previous editions)

Datasheet last updated 5/9/2025 6:38:20 AM (supersedes all previous editions)

Figure 10. A compilation of laboratory test data and practical results for different stainless steels in aerated, aqueous chloride environments. Intergranular corrosion The TTC diagram, figure 11, shows results of intergranular corrosion testing according to ASTM G-28 (120 hours in boiling iron(III)sulphate and sulfuric acid solution). As the figure illustrates, Sanicro® 28 can be kept in the critical interval of 600-700°C (1100-1300°F) for at least 30 minutes without intergranular corrosion occurring in this highly corrosive medium. As can be seen in figure 11, Alloy 904L is more susceptible to...