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PRODUCT USES WSC 8820 is an exceptionally effective, concentrated liquid scale and corrosion inhibitor. It is designed for use in a wide range of open recirculating cooling water systems where clean, scale and deposit-free surfaces are required for maximum system life and efficiency. WSC 8820 accomplishes this with one easy to use product, without the need of the synergistic use of a scale inhibitor. WSC 8820 contains a special blend of anodic and cathodic corrosion inhibitors, designed to inhibit corrosion of ferrous metals by creating a passivating barrier. A specific inhibitor is included also to protect copper alloys from corrosion. WSC 8820 is used for corrosion and scale control in systems with corrosive or high scaling makeup water and system operating conditions.
DESCRIPTION
WSC 8820 is very effective also in low hardness, low alkalinity corrosive waters. It contains special filming ingredients to establish protective barriers against corrosion on ferrous metal surfaces. It also contains special filming ingredients to establish a protective barrier against corrosion and pitting on both yellow metal and ferrous metal surfaces. WSC 8820 is environmentally safe for discharge with the cooling system bleedoff. The formulation contains no heavy metals, chromates, or other pollutants requiring removal or treatment prior to discharge at normal usage rates. Molybdate does not provide a nutrient source as do many other corrosion inhibitors. This eliminates a food source for algae and bacteria in the water system and makes control of microorganisms easier at lower microbiocide dosage rages. WSC 8820 may be used alone as a single product for control of corrosion in systems where hardness and alkalinity does not pose a scaling problem, or in high hardness and/or high alkalinity waters where higher cycles of concentration and lower bleed rates are desired.
BENEFITS
TECHNOLOGY Open recirculating cooling systems can include mild steel, galvanized steel, stainless alloys, copper and copper alloys, and aluminum. These metals are subject to a range of corrosion problems such as generalized corrosion, galvanic attack, pitting, crevice attack and stress cracking WSC 8820 is designed for systems using makeup water of moderate hardness and alkalinity, and discharging to a city sewer or other treatment plant. Corrosion protection is provided through the use of molybdate, phosphonate, and azole compounds which have been shown in tests to be superior to most corrosion inhibitors available, and throughout a broad pH range.
Sodium molybdate has been used for decades as a substitute for chromates for the inhibition of corrosion in mild steels over a wide range of pH. Molybdates have a very low toxicity and are less aggressive oxidants toward organic additives that are often used in corrosion inhibiting formulations. The protection of mild steel used in the construction of air-conditioning cooling water and heating systems is a prime application. Molybdate solutions protect against rusting of steel parts during machining, and are used in water based hydraulic systems. It is also used as an additive in automobile engine anti-freeze.
Molybdate (MoO4=) is a good corrosion inhibitor for open systems because it neither reacts with oxygen nor evaporates. Molybdate bonds tightly to metal atoms, especially in the presence of dissolved oxygen. The tenacious molybdate-metal complex is continuous over the entire surface and impervious to oxygen, so oxidative corrosion (rusting) is inhibited. In the presence of nitrogen was found to enhance the
formation of molybdate Molybdate inhibits steel, cast iron, aluminium, copper, brass, cadmium and solder, and is usually used synergistically with other corrosion inhibitors.
Control of copper corrosion is critical. While copper and its alloys are quite corrosion resistant, the impact of even low corrosion rates can be dramatic. When copper corrodes, soluble copper ions plate out onto mild steel components. When this happens, the more inert copper metal becomes a “permanent” cathode on the metal surface. At this point, the corrosion process, which had been spread over the entire steel surface, now becomes localized and continues at an accelerated rate. As this proceeds, instead of having a low general corrosion rate, high local corrosion rates will be seen.
In contrast to precipitating agents, the nitrogen atoms in the azoles bond to the copper metal via copper oxide molecules on the surface. The protective layer that is formed enhances the natural corrosion resistance of copper and copper alloys .Polymers can distort the crystal growth of the scale by disrupting the crystalline lattice which causes the hard dense adherent nature of scales. With the inclusion of a relatively large, irregularly shaped polymer in the crystalline lattice, scale does not develop or adhere to surfaces where it could cause heat transfer problems. The polymer prevents normal scale development and disperses the more amorphorus material which may form. The effectiveness of polymers in scale control has changed the nature of many cooling water treatment programs by allowing high cycles and/or high pH conditions to be used.
DOSAGE WSC 8820 dosages may vary somewhat according to operating conditions, but generally 50-125 ppm of WSC 8820 should be maintained in the system water. (This is equivalent to about ˝ to 1 pint of WSC 8820 per 1000 gallons of water.)This dosage should be tripled for a two-week period when initiating treatment, whenever the system is refilled with fresh water, and after any major system upsets, in order to establish effective corrosion control. If the stability index of the recirculated water is higher than 10.5, an alkalinity booster such soda ash should be fed to reduce the index to less than 10.5.
WSC 8820 is controlled by a molybdate test which provides easy and accurate control readings. Maintain 2 to 5 ppm MoO4= at all times.
WSC 8820 must be fed continuously to the system by a positive displacement chemical feeder. For maximum results, feed should be linked to makeup of bleedoff through the use of a flowmeter or conductivity controller.Residuals are adjusted and maintained by chemical test of the system to provide a residual of 2-5 ppm MoO4=. Your Water Services Ltd representative is available to give recommendations on the application, monitoring, and control of this product for optimum results.
HANDLING WSC 8820 is relatively mild material, avoid contact with eyes and skin, should contact occur, flush with water. If discomfort persists, seek medical attention. Do not take internally. Do not freeze, Store at moderate temperature. Keep container closed.Read Material Safety Data Sheet for detailed handling and storage precautions.
TECHNICAL ASSISTANCE
USDA This product is USDA G7. OTHER REMARKS Improper application of this product will result in insufficient protection and/or potential damage to the system being treated. Please follow the recommendations of your Water Services Ltd representative. |
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PROTECTS
against galvanic corrosion in mixed-metal systems.
oxyanions.
These oxyanions deposited back onto the anode surfaces as insoluble salts formed
with iron cations released from the anion electrode. The increased formation of
oxyanions is postulated to be the result of deprotonation of electrolyte in
contact with the anion electrode, and a subsequent shift in pH to higher values.
In addition to acting as a kinetic barrier, the oxyanionic species act as an
electrostatic barrier to the ingress of the Cl- anions which cause pitting. So WSC
8820 is particularly effective against pitting corrosion.
