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GENERAL INDICATORS OF CORROSIVE WATER

1. Low pH: If the pH is less than 7.0 an acidic and corrosive condition is  indicated.

2. Dissolved oxygen concentration greater than 2 ppm (probably occurs in shallow water table aquifers).

3. Hydrogen sulfide concentration at less than 1ppm.

4. Total dissolved solids greater than 1000 ppm(leads to electrolytic corrosion).

5. Carbon-di-oxide concentration greater than 50 ppm.

6. Chloride concentration greater than 500 ppm.

GENERAL INDICATORS OF ENCRUSTING WATER

1. pH greater than 7.5

2. Carbonate hardness greater than 300 ppm (deposition of Calcium Carbonate)

3. dissolved iron concentration greater than 2ppm.

4. Dissolved managers concentration greater than 1 ppm.

Corrosion is the major problem in steel casing and screens. Corrosion results from chemical and electrochemical processes. Chemical corrosion occurs when a particular constituent is present in water, in sufficient concentration, to cause rapid removal of material over broad areas. Commonly, these constituents are carbon dioxide, oxygen, hydrogen sulfide, hydrochloric acid, chloride and sulfuric acid. Chemical corrosion can cause severe damage in steel wells, regardless of the amount of total dissolved solids.

However, the number of wells affected by the chemical corrosion is small in comparison to wells affected by electro-chemical corrosion.

WHAT IS ELECTRO-CHEMICAL CORROSION ?

Electro-Chemical corrosion can be described as the flow of an electric current which facilitates the corrosive attack on metal. For this to happen, two conditions are necessary. :

Electro-chemical corrosion can be described as the flow of an electric current which facilitates the corrosive attack on metal. For this to happen, two condition are necessary :

1. A difference in electrical potential on metal surfaces &

2. Water containing enough dissolved solids to be a conductive fluid (Electrolyte).