Materials of Construction

Material	Advantage		Disadvantage
Carbon Steel	Low cost, easy to fabricate, abundant, most common material.  Resists most alkaline environments well.		Very poor resistance to acids and stronger alkaline streams.  More brittle than other materials, especially at low temperatures.
Stainless Steel	Relatively low cost, still easy to fabricate.  Resist a wider variety of environments than carbon steel.  Available is many different types.		No resistance to chlorides, and resistance decreases significantly at higher temperatures.
254 SMO (Avesta)	Moderate cost, still easy to fabricate.  Resistance is better over a wider range of concentrations and temperatures compared to stainless steel.		Little resistance to chlorides, and resistance at higher temperatures could be improved.
Titanium	Very good resistance to chlorides (widely used in seawater applications).  Strength allows it to be fabricated at smaller thicknesses.		While the material is moderately expensive, fabrication is difficult.  Much of cost will be in welding labor.
Pd stabilized Titanium	Superior resistance to chlorides, even at higher temperatures.  Is often used on sea water application where Titanium's resistance may not be acceptable.		Very expensive material and fabrication is again difficult and expensive.
Nickel	Very good resistance to high temperature caustic streams.		Moderate to high expense.  Difficult to weld.
Hastelloy Alloy	Very wide range to choose from.  Some have been specifically developed for acid services where other materials have failed.		Fairly expensive alloys.  Their use must be justified.  Most are easy to weld.
Graphite	One of the few materials capable of withstanding weak HCl streams.		Brittle, very expensive, and very difficult to fabricate.  Some stream components have been know to diffusion through some types of graphites.
Tantalum	Superior resistance to very harsh services where no other material is acceptable.		Extremely expensive, must be absolutely necessary.