Stainless Steel Alloy 316 UNS S31600 By yaang.com

Stainless Steel 316 is molybdenum-bearing austenitic stainless steel. The higher nickel and molybdenum content in this grade allows it to demonstrate better overall corrosion resistant properties than 304, especially with regard to pitting and crevice corrosion in chloride environments. In addition, Stainless Steel Alloy 316 provides excellent elevated temperature tensile, creep and stress-rupture strengths, as well as outstanding formability and weldability. Stainless Steel Alloy 316 is immune from sensitization; therefore, it is very frequently used in heavy gauge welded components.

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.

Selection of Stainless Steel for Handling Phosphoric Acid H3PO4 By yaang.com

Phosphoric Acid is also know as orthophosphoric acid and is classed as a weak acid. Austenitic stainless steel have goodcorrosion resistance to chemically pure phosphoric acid. Wet process phosphoric acid (WPA) can be aggressive.

It is used as a chemical-cleaning agent for stainless steel but is not considered to be a 'passivating' acid.

Bi-Metallic Corrosion Galvanic Corrosion By yaang.com

Bi-Metallic corrosion Galvanic Corrosion is the additional corrosion that occurs when dissimilar metals are in contact in the presence of an electrolyte. The corrosion of a metal, the anode, results from the positive current flowing from the anode to the less reactive (more noble) metal, the cathode, through the electrolyte. 
This process is similar to the conventional corrosion of a single, uncoupled metal but generally proceeds at a higher rate depending on the difference in electrochemical reactivity of the anode and cathode metal.

Stainless Steel 316 And Stainless Steel 316L Technical Data By yaang.com

Stainless Steel 316 or Stainless Steel 316L is an improved version of stainless steel 304, with the addition of molybdenum and a slightly higher nickel content. The resultant composition of stainless steel 316 gives the steel much increased corrosion resistance in many aggressive environments. The molybdenum makes the steel more resistant to pitting and crevice corrosion in chloride-contaminated media, sea water and acetic acid vapours. The lower rate of general corrosion in mildly corrosive environments gives the steel good atmospheric corrosion resistance in polluted marine atmospheres.