Selection Stainless Steel for Handling Sulphuric Acid H2SO4 By yaang.com

Sulphuric acid is oxidising when concentrated but is reducing at low and 'intermediate' concentrations.

The response of most stainless steel types is that in general they are resistant at either low or high concentrations, but are attacked at intermediate concentrations. Commercially concentrated acid is around 96 wt % (sg = 1.84).

The improvement in corrosion resistance moving from stainless steel 304 /1.4301 to 316 / 1.4401 is due to the addition of molybdenum. Further additions of moybdenum and copper in the 1.4539 904L grade extend the corrosion resistance in these reducing acid conditions. The molybdenum in types 316 stainless steel and grade 1.4539 also helps improve resistance to chloride attack, when present as impurities in the acid.

Selection of Stainless Steel for Handling Ammonia NH3 By yaang.com

Ammonia at normal atmospheric temperature and pressure is a gas. It can be stored under pressure as a liquid or below it's atmospheric boiling point of -34 degC.

It has been assumed that there is no corrosion risk to stainless steel that are normally considered for the storage and handling of bulk ammonia (ie stainless steel 304 or stainless steel 316 types) although there does not appear to be any published data to substantiate this. The general corrosion resistance of the 304 types should be adequate for installations at most sites, but for coastal or marine sites stainless steel 316 should be considered if the outer-casing or parts are exposed.

Selection of Stainless Steel for Handling Citric Acid C3H4OH (COOH)3 By yaang.com

Citric acid is a weak organic acid, found in fruits such as lemons (citrus)

Either the stainless steel 304 or stainless steel 316 types can be considered for most storage and handling applications. Citric acid is also be used forcleaning stainless steel and passivating stainless steel.

The low carbon types (304L stainless steel or 316L stainless steel) may be needed for temperature above around 60 degC to avoid any risk of intergranular attack in weld heat affected zones.

Stainless Steels Sorting and Identification Tests By yaang.com

Stainless Steels Sorting and identification tests are non-destructive, inexpensive and rapid procedures, usually carried out on different grades of stainless steels. Sorting of product procedures is particularly useful when Stainless Steel bars of Stainless Steel grade 303 and 304 have been accidentally stored together, or when Stainless Steel grade 304 and Stainless Steel 316 sheet offcuts are mixed.

Although these tests are extremely useful, they have certain limitations too. It is difficult to sort one heat from another of the same grade using these tests. For instance, type stainless steel 304 cannot be readily sort from stainless steel 321, stainless steel 316 from stainless steel 316L or stainless steel 304 from stainless steel 304L.