Corrosion, whether in the atmosphere, underwater, or underground, is caused by the flow of electricity from one metal to another metal, or from one part of the surface of a piece of metal to another part of the same metal where conditions permit the flow of electricity. For this to occur there must be a moist conductor or electrolyte present for the flow of energy to take place.

Compound, which capable of donating free chlorine ions in aqueous solution, has the potential for causing failure in stainless steels. Chlorine ion is electronegative and very reactive with certain compounds and elements. This reactivity is part of its usefulness in certain situations, but becomes a double-edged sword where stainless steel is concerned. In many ways chlorine can be introduced into a piping system and the most common seen in food industry applications are as salt (NaCl) and in chlorine-based sterilising solutions such as bleach (NaOCl) Salt water (brine) is known to corrode stainless steel, as is bleach.

When iron rusts, the attack is fairly uniform over the surface exposed to the corrosive environment. Chloride attack of stainless steel is exactly the opposite crevices and pits form and grow perpendicularly to the surface being attacked, rather than spreading out evenly as rust does. Some areas may appear essentially untouched by the corrosion, while others will be severely attacked. This means that thicker tubes and pipes will not necessarily last much longer than thin ones before failing due to chloride induced corrosion.

Stainless steel is very corrosion resistant. Water supplies will usually have chlorine or hydrochloric acid added to prevent bacterial growth, it is important to use a material that will resist corrosion by such harsh chemicals. 316 stainless is highly effective in resisting this corrosion.

Stainless steel dissolves very slowly in water, even reverse osmosis/RO water, so only a very small amount of chemical compound elements are added to the water. Using plastic, copper, or iron allows all kinds of unknowns to be added to the water. Plasticiser, from certain plastics, can be leached into the water system, especially when aggressive RO water is used.

Stainless steel is a very clean material and can be sanitised easily. If dead spaces are minimized and surfaces polished to eliminate crevices and pits, bacteria growth is minimized.  This is especially true when the piping system is flushed or has continuous water circulation at velocities high enough to cause turbulent flow. Turbulent flow is important because the turbulence creates a scouring of the pipe surface. Low flow or laminar flow leaves a stagnant film of water next to the pipe surface and a biofilm can form.

Since corrosion resistance is a primary reason for the use of stainless steels, a basic understanding of the types of corrosion and how they occur is important.