Service inhibitors

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials No reactions Stability During Transport Stable Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Polymerization is accelerated by heat and exposure to oxygen, as well as the presence of contamination such as iron rust. Iron surfaces should be treated with an appropriate reducing agent such as sodium nitrate, before being placed into isoprene service Inhibitor of Polymerization Tertiary butyl catechol (0.06 %). Di-n-butylamine, phenyl-beta-naphthylamine andphenyl-alpha-naphthylamine are also recommended. 

Almost all premium lubricants are so-called paraffinic oils composed primarily of both paraffinic and aUcycUc stmctures, with only a minor portion of aromatics. When stabilized with an oxidation inhibitor and fortified with other appropriate additives, these paraffinic—aUcycUc compositions provide nonsludging oils that are satisfactory for almost any type of service. 

Cyclohexylamine is miscible with water, with which it forms an azeotrope (55.8% H2O) at 96.4°C, making it especially suitable for low pressure steam systems in which it acts as a protective film-former in addition to being a neutralizing amine. Nearly two-thirds of 1989 U.S. production of 5000 —6000 t/yr cyclohexylamine serviced this appHcation (69). Carbon dioxide corrosion is inhibited by deposition of nonwettable film on metal (70). In high pressure systems CHA is chemically more stable than morpholine [110-91-8] (71). A primary amine, CHA does not directiy generate nitrosamine upon nitrite exposure as does morpholine. CHA is used for corrosion inhibitor radiator alcohol solutions, also in paper- and metal-coating industries for moisture and oxidation protection. 

Service Life. The service life offered by a coolant is dependent on many factors, including the initial condition of the coolant and the cooling system, the type of water used for dilution, the metals of constmction in the system, the type of corrosion inhibitors and SCAs used, the system operating... 

Despite all these safeguards to extend the service life of the antifreeze, fluid replacement is requited periodically. Typically, fluids are replaced because of irreversible damage caused by one of four conditions contamination, gel formation because of glycol/siUcate reaction, extensive glycol degradation caused by overheating or excessive oxygen exposure, or inhibitor depletion. 

The freezing point of the coolant should be monitored for coolants in all types of service. Additionally, maintenance of the corrosion inhibitor levels is requited of the heavy-duty service coolants and the stationary engine coolants. Because corrosion inhibitors and combinations of corrosion inhibitors work most effectively at given concentrations and specific ratios to the other inhibitors, appropriate concentrations must be maintained to maximize corrosion protection. Many manufacturers of coolants for stationary engines, and manufacturers of SCAs, provide an analytical service to monitor the effective inhibitor concentrations in the system periodically. Recommendations can then be made for proper maintenance and inhibitor replenishment. 

Ethanol water is a solution of denatured grain alcohol. Its main advantage is that it is nontoxic and thus is widely used in the food and chemic industry. By using corrosion inhibitors it could be made non-corrosive for brine service. It is more expensive than methanol water and has somewhat lower heat transfer coefficients. As an alcohol derivate it is flammable. 

In styrene service, vapor may condense in flame arresters, and the liquid formed is low in inhibitor. Liquid may polymerize and plug off the arrester. Possible solutions include cleaning the arrester frequently or using a PVRV (pressure-vacuum relief valve). 

Cost of inhibitors, extra control facilities, and so on, required to assure achievement of predicted service life... 

Corrosion-inhibiting primers based on this technology have been in continuous service since they were first utilized with nitrile epoxies in the late 1960s. These inhibitors function by passivating the aluminum. In this process, water permeating the adhesive bondline carries a certain amount of inhibitor to the oxide surface. 

Microbiocides may be toxic to humans therefore, care must be taken when used. When selecting the microbiocide, the field engineer can obtain pertinent information on chemicals from the service company providing the chemicals. The microbiocide selected must be compatible with the system in which it is being used. Some chemicals such as quaternary amines have dual functions one as microbiocides and the other as film-forming corrosion inhibitors. Insufficient concentrations of this type of chemical may not be enough to coat the whole surface of metal and can cause pitting corrosion. The selection must also depend on chemicals that can produce the desired control in minimum time limits and... 

Viewed in perspective, evidence of failure in service has been rare and the practical hazard is certainly very much lower than would appear from the results of laboratory tests. In chlorinated hydrocarbons the effect can be controlled by the addition of inhibitors, and, for example, the appropriate commercial degreasants containing these inhibitors are specified in a British detence standard. ... 

A common feature of both these methods is that the quantity of treatment chemical can be calculated from stoichiometric relationships in the reactions involved. This is not so with conventional inhibitor treatments. With these the concentration of inhibitive chemicals can only be determined on the basis of experimental laboratory studies, service trials and overall practical experience. 

Even with adequate cleaning procedures it is still necessary to ensure that the inhibitor reaches all parts of the metal surfaces. Care should be taken, particularly when first filling, a system, that all dead ends, pockets, crevice regions, etc., are contacted by the inhibited fluid. This will be encouraged in many systems by movement of the fluid in service but in nominally static systems it will be desirable to establish a flow regime at intervals to provide renewed supply of inhibitor. 

Britton, C. F., The Selection, Evaluation and Testing of Oil Field Corrosion Inhibitors , Seminar The Development and Use of Corrosion Inhibitors , Oyez Scientific and Technical Services Ltd., London (1983)... 

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