Sandvik special steel fights nitric acid corrosion

Citation

(1999), "Sandvik special steel fights nitric acid corrosion", Anti-Corrosion Methods and Materials, Vol. 46 No. 3. https://doi.org/10.1108/acmm.1999.12846cab.014

Sandvik special steel fights nitric acid corrosion

Sandvik special steel fights nitric acid corrosion

Keywords Acids, Corrosion resistance, Sandvik, Stainless steel

Specially developed for use in nitric acid plants, Sandvik Steel is reporting continued and increasing demand, for replacement and new build applications, for tubes produced in its stainless steel grade Sandvik 2RE10.

Stainless steel has always been the traditional material of construction in nitric acid plants and standard stainless steel grades, for example AISI 304L, are commonly used in all parts of the plant where nitric acid is present. However, in areas of the plant exposed to more aggressive conditions, such as coolers or condensers, Sandvik's special grade 2RE10 is being used to minimise corrosion.

Sandvik 2RE10 is an austenitic stainless steel with high chromium (25 per cent) and low carbon and impurity contents. According to Sandvik it is characterised by excellent resistance to nitric acid and intergranular corrosion and good resistance to pitting. It also claims good weldability. No preheating is said to be required. Suitable welding methods are manual metal-arc with covered electrodes and gas-shielded arc welding. TIG and MIG methods are recommended.

The major benefit claimed of Sandvik 2RE10 tubing is that it resists corrosion when condensing and reboiling occurs. In coolers and condensers, this corrosion is normally encountered at the inlet end where the first condensate is formed. The higher the operating temperature and pressure, the greater the risk of reboiling occurring, resulting in very aggressive local acid attack Sandvik 2RE10 has reportedly shown excellent resistance with gas inlet temperatures up to 210°C.

In tail gas preheater applications, droplets of nitric acid are drawn into the tail gas from the absorption tower. When the gas enters the heater, the droplets settle on the hot tube wall and boil. The temperature of the heating medium, usually hot gas or steam can be very high. This can lead to conditions where 2RE10 is believed to be a preferred material in place of titanium.

Depending on operating conditions, Sandvik can demonstrate service life in years for 2RE10 tubes compared to months for standard stainless steel grades. Details from Sandvik Steel, UK. Tel: +44 (0)121 504 5100; Fax: +44 (0)121 504 5151; Web: www.steel.sandvik.com