Essay Effect of Ph Level on Corrosion Rate

2020 Words May 27th, 2013 9 Pages
THE EFFECT OF pH LEVEL ON CORROSION RATE A Long Laboratory Report Presented To; The Department of Chemical Engineering BY IGBOKWE C.E (Group C) 090401024 …show more content…
A higher pH means there are fewer free hydrogen ions, and that a change of one pH unit reflects a tenfold change in the concentrations of the hydrogen ion. For example, there are 10 times as many hydrogen ions available at pH 7 than at pH 8. The pH scale commonly quoted ranges from 0 to 14 with a pH of 7 considered to be neutral.
Substances with a pH less that 7 are considered to be acidic and substances with pH equal to or greater than 7 to be basic or alkaline. Thus, a pH of 2 is very acidic and a pH of 12 very alkaline. However, it is technically possible to have very acidic solutions with a pH lower than zero and concentrated caustic solutions with a pH greater than 14. Such solutions are in fact typical of many ore extracting processes that require the digestive power of caustics and acids.
Low pH acid waters accelerate corrosion by supplying hydrogen ions to the corrosion process. Although even absolutely pure water contains some free hydrogen ions, dissolved carbon dioxide (CO2) in the water can increase the hydrogen ion concentration. Dissolved CO2 may react with water to form carbonic acid (H2CO3) as shown in equation. where Keq is the reaction equilibrium expressed as a ratio.
Carbonic acid subsequently dissociates in bicarbonate and carbonate ions as expressed respectively in the following equations:

Rust Chemistry
Rusting of iron consists of the formation of

Related Documents