ACT Zinc-Loc Pgm
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Heavy Metal




Risk Management falls into many categories, "Metal Eating Bacteria" and "White Rust" are no exceptions.

Throughout the United States, "metal-eating" bacteria have already infected thousands of cooling towers and will threaten many more, if ignored! Detection is very difficult, and failure to stop this condition can lead to the total destruction of a cooling tower. Microbiologically influenced corrosion (MIC) is a result of destructive microorganisms that produce sulfuric acid, hydrogen sulfide, or other corrosive materials that can corrode metal. This is especially true in areas of low flow such as crevices at the bottom and sides of a cooling tower sump or small tubes in heat exchangers.

In conjunction with MIC, "White Rust" is another serious problem nearing epidemic proportions. White rust consist of a thick, off white waxy solid, that is a result of rapid deterioration of the protective galvanized coating in a cooling tower, and can lead to a total loss within a few years if left unchecked. The proactive nature of ACT's Risk Control Program can prevent these "investment destroyers".

MIC and white rust not only eat away at cooling towers and heat exchangers, they can devour substantial sums of money in the form of increased electrical costs due to poor heat transfer, and increased cost for repairs or replacement. In fact, experts attribute many millions of dollars in equipment damage each year to corrosion by microorganism attack. This is true for cooling towers and the complete water system.

Both MIC and white rust are relatively new maladies that have escalated to epidemic proportions locally due to three factors: 

1. Due to environmental concerns, the EPA has banned the use of highly toxic heavy metal corrosion inhibitors, that help mitigate detrimental microorganism growth.

2. Stringent regulations on the use of lead have prompted the reduction of lead content in the galvanizing process, causing the coating to degrade at higher a pH making white rust more common.

3. Water conservation and environmental regulations have prompted Public Water Authorities to raise the pH levels of local water supplies, to reduce the corrosion rate of lead solder joints in water lines, thereby reducing the lead content in domestic drinking water. The resulting increased pH feeds white rust and reduces the effectiveness of biocides that inhibit the spread of MIC.

Additional proactive Risk Control measures may be taken to prevent MIC, but none are 100% guaranteed to prevent the growth of this acidic slime. MIC coats the metal surfaces of a cooling tower, preventing corrosion control chemicals from protecting the galvanized metal. The MIC coating is actually a slime created by the buildup of waste products from bacteria. White rust is formed when the zinc coating is submerged in cooling tower water, and combines with carbonate in the water to form a zinc carbonate which causes rapid deterioration of the metal. Under ideal conditions a protective coating of reacted zinc corrosion products consisting of insoluble zinc salts and salts of water soluble cations is formed over the galvanized steel interior of a cooling tower.

The best protection is an educated owner, property manager, engineering manager, or building engineer ; and to learn more about the dangers of these two, and other cooling tower plagues, how to prevent them, the liabilities and insurance concerns involved, contact Advanced Chemical Technology, Inc. at, 800.527.9607, or E-Mail: