Cured Purethane Coatings are highly inert, unaffected by water, non-toxic, odour & tasteless and non-conducive to bacterial growth. They have a negligible leach rate of TOC (Total Organic Compound). Combined with their excellent corrosion protection, these features allow them to be used extensively in Potable Water production and transmission.
Purethane is finding extensive use in lining raw and potable water pipelines. Steel & concrete clarifiers & holding tanks in potable water production facilities are protected by lining with Purethane Coatings. Purethane lined elevated distribution water towers are easy to clean.
The internal corrosion of pipes and fittings can have a direct impact on the concentration of some water constituents including Cadmium, Copper, Iron, Lead, and Zinc. Corrosion control is therefore an important aspect of management of a water supply system. (WHO , GENEVA " Guidelines To Drinking Water Quality, 1992). This can be prevented by lining with Purethane Coatings.
Cement mortar traditionally used to line potable water pipes is increasing finding disfavour and being replaced by Purethane Coatings due to the following factors:
- Cement mortar lining has a very cumbersome curing method with slow production rates. Any improper curing may lead to cracking in the lining. Purethane coatings on the other hand are very fast curing and allow high production rates.
- Cement mortar has ZERO bond with the steel core and is held in place only by compression. Purethane coatings on the other hand have high adhesion to the steel surface.
- Impact resistance is only of the order of 2 Inch Lbs compared to > 200 Inch Lbs of Purethane coatings.
- Poor corrosion resistance. Cement Mortar passes < 1,000 Hours of Salt Spray compared to > 10,000 Hours for Purethane Coatings.
- Reduction in pipe diameter and capacity of Cement Mortar lined pipes due to high thickness.
- Rougher surface with ? = 0.3 – 3.0 mm compared to ? = 0.00065 mm for Purethane coatings. This leads to higher friction and consequent Head /Pumping losses.
- Cement is subject to deterioration on prolonged exposure to aggressive water - either due to the dissolution of lime and other soluble compounds or to chemical attack by aggressive ions such as chloride or sulfate - this may lead to structural failure of the cement pipe. A pH of 8.5 or higher may be necessary to control cement corrosion. Purethane on the other hand have high chemical resistance.