Sulfur dioxide will combine with condensed water to form sulfurous acid. If there is an electrical potential difference between two dissimilar metals, and a conductive solution of some substance dissolved in water exists between the two metals, then electrolytic or galvanic corrosion can occur. And in situations where lubrication is present, additional chemical reactions will occur and further compound the issue. The following chart demonstrates some examples of corrosive gases, their sources, and the materials they affect. While all corrosive gases listed below are harmful to air compressor components, the materials most susceptible to corrosive attack are copper, aluminum, and cast steel.
Cast steel is used for many centrifugal compressor components such as the casing and some diffusers.
Aluminum is used for diffusers and copper is commonly used for intercoolers. The most susceptible components in a centrifugal air compressor are usually the coolers. Corrosive Gas Hydrogen fluoride Source aluminum manufacturing, steel manufacturing, ceramics manufacturing, electronic device manufacturing, fertilizer manufacturing, and fossil fuels. Metals Affected copper, tin, silver and iron alloys Hydrogen fluoride reacts in the same manner as an inorganic chloride compound even though it is a member of the halogen family. Active sulfur compounds will readily attack the above listed metals, even at low concentrations.