Nickel-molybdenum steels

Most HPLC columns are made of 316 grade stainless steel, which is austenitic chromium-nickel-molybdenum steel, USA standard AISI, resistant to the usual HPLC pressure and also relatively inert to chemical corrosion (chloride ions and lithium ions at low pH being important exceptions). The inside of the column should have no rough surfaces, grooves or microporous structures, so the steel mbes must be either precision drilled or polished or electropolished after common manufacturing, e.g. by drawing. 

FIGURE 20.24 Pitting potential Up of austenitic chromium-nickel nickel-molybdenum steels in a NaCl solution as a function of the PRE. 

Factors affecting pitting corrosion in austenitic chromium-nickel-molybdenum steels are listed in Table 20.2. 

Precipitation processes of this kind are always caused by heat treatments, snch as sensitizing annealing, that are inappropriate for the alloy in question. For the austenitic chronuum-nickel-molybdenum steels used for the fabrication of chemical plant equipment, the critical tanperature range is 400-800°C. Chromium depletion through formation of chromium-rich carbides, mostly of the type (M23Cg), is the main cause of intergranular corrosion in these steels. The precipitation of chromium nitrides of importance only that the chromium-rich nitride (CrjN) can initiate intergranular corrosion, especially in ferritic steels. Since the intermetalUc phases in stainless steels contain appreciably less chromium than carbides and nitrides and their deposition is far slower, the chromium depletion related to these phases is minimal. 

On the corrosion behaviour of austenitic chromium-nickel-(molybdenum) steels with and without addition of nitrogen with special consideration of their strain in chloride containing solutions)... 

The influence of nitrogen on the corrosion chemical properties of solution-annealed and annealed austenitic 18/10 chromium-nickel-molybdenum steels. 

A Study was carried out with a large number of individual and mixed waste waters in test plants at pressures of 150-200 bar, temperatures of 543-603 K (270-330 °C) and with variations of the chloride, sulphate, and phosphate concentrations, the pH values as well as the COD values (Chemical Oxygen Demand). The following metallic materials were examined in this study with regard to their suitability in wet oxidation plants for industrial waste waters chromium-nickel-molybdenum steel 1.4571 (X6CrNiMoTil7-12-2), titanium, tantalum, and nickel. None of the investigated materials was resistant at acidic pHs. At pH values > 7, titanium and tantalum were resistant, even in the presence of low fluoride concentrations and chloride concentrations of up to 100 g/1 [50]. 

The immersion motor pumps that were made of chromium-nickel-molybdenum steel SAE 316, 1.4401 (X5CrNiMol7-12-2) were compared to those made of cast iron. In addition to a better corrosion resistance, the CrNiMo steel pumps also have the advantage of a smooth and poreless surface and can thus be cleaned more easily if used in waste water treatment tanks [13]. 

The austenitic chromium-nickel-molybdenum steel UNS N08904 (1.4539, XlNiCrMoCu25-20-5) has proven suitable as a material for the head cooler of stripper units used in waste water treatment plants of refineries [26]. The operating parameters are summarised in Table 18. 

The chromium-nickel-molybdenum steels 1.4571 (SAE 316 Ti, X6CrNiMoTil7-12-2) and particularly 1.4435 (SAE 316 L, X2CrNiMol8-14-3) are resistant to crevice corrosion, which can occur under the operating conditions in a digester if steels with lower alloy contents are used. The importance of the correct constructive design as well as the elimination of welding tarnishes by pickling is discussed [58]. 

Alloy 600 Alloy 625 Alloy 690 Alloy 718 Alloy 800 Alloy 926 Alloy B-2 Alloy B-4 Alloy C-4 Alloy C-22 Alloy C-276 AIMg4.5Mn 192 AIMg4.5Mn0.7 189,191-192 aluminium 183-184,291 austenitic chromium-nickel-molybdenum steel 104,334... 

Structural steels with up to 12% chromium 104 Ferritic chromium steels with more than 12% chromium 104 Ferritic-austenitic steels with more than 12% chromium 104 Austenitic chromium-nickel steels 104 Austenitic chromium-nickel-molybdenum steels 104 Austenitic chromium-nickel steels with special alloying additions 104 Zinc 112 Bibliography 147... 

Steel, particularly stainless steel, is the material most often used today for manufacturing fermentors. Two categories of stainless steel exist one contains molybdenum the other does not. Chrome-nickel-molybdenum steel is more resistant to corrosion and it is necessary for the long-term conservation of sulfited white wines, especially in partially filled tanks in the humid atmosphere above the wine, sulfur dioxide gas is concentrated and the condensation formed on the tank walls is corrosive. For red winemaking and storage in completely filled tanks, the less expensive chrome-nickel steel is sufficient. 

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