Inhibitors oxygen scavengers

Uses Reducing agent corrosion inhibitor wastewater treatment electrolytic plating redox reactions polymerization catalyst organic hydrazine derivs. rocket propellant corrosion inhibitor, oxygen scavenger in boiler... 

Performance of biological control formulations in the system can be affected by other chemical control programs (e.g. oxygen scavengers, some corrosion inhibitors). Oxygen scavengers and biocide formulations are usually incompatible. Widely separated injection points are advisable. 

Uses Corrosion inhibitor, demulsifier, pour pt. depressant, paraffin inhibitor, paraffin solvent, bactericide, scale inhibitor, oxygen scavenger, antilbamforoil and gas prod. coagulant, flocculant for water treatment fuel additive, process additive in refining... 

Oxygen Scavenger Corrosion Inhibitor Figure 10.23 Injection water treatment scheme... 

Chemical treatment programs are often individually designed for particular boiler plant systems but usually contain oxygen scavengers, pH boosters, and corrosion inhibitors. In addition, the formulations employ materials specifically designed to limit the degree of deposition and control the mechanisms of deposition. 

Here, the use of inhibitor formulations having a less dramatic effect on TDS (such as certain tannins) may be extremely beneficial. Formulations are available that are based on tannin chemistry and contain blends that act as oxygen scavengers and metal passivators, with additional sludge dispersant and antifoam properties. 

Where water softening is provided and there is no reduction in system water TDS, treatments are primarily based on inorganic corrosion inhibitor blends (nitrite, molybdate, etc.). Under these circumstances, there is no benefit in using an expensive organic oxygen scavenger to keep the TDS level low, and a common chemical such as catalyzed sodium sulfite may be used. 

Water losses and other problems result in periods of undertreatment of both oxygen scavengers and corrosion inhibitors and remain unexplained and uninvestigated. 

Chapter 11 completes the discussion on internal treatment programs with information on program primary support chemicals, including oxygen scavengers and condensate treatments (vapor phase inhibitors) and adjuncts. 

As a consequence, it is not possible to devise a single class of anodic inhibitor formulation that satisfies all water treatment requirements. Rather, there several types of formulations, and some formulators may offer each of these products in different strengths, with or without oxygen scavengers and indicator dyes in their blends. As examples, a nitrite/sUicate formulation and a molybdate/nitrite formulation are provided here ... 

Alkalinity boosters, which are vitally necessary to enable carbonate, phosphate, balanced polymer (polymer plus phosphate or chelant), and some other program types to function, are perhaps best described as conjunctional treatments, whereas oxygen scavengers, antifoams, and condensate line corrosion inhibitors are adjuncts. Programs such as phosphate-tannin mixtures are sometimes described as adjunct treatments. The chemistries and applications of various types of conjunctional treatments and adjuncts are described in this chapter. 

Alkaline oxygen scavengers may be used as alternative treatments to some corrosion inhibitors where toxicity restrictions prohibit proprietary blends. 

A further longer term wet lay-up alternative is through the use of volatile corrosion inhibitors (VCIs) such as dicyclohexylamine acetate. These are dissolved in the water at a temperature below 60 °C, and the water is circulated for 4 to 5 hours. The boiler does not need to be completely filled because the VCI migrates to all parts of the boiler and reaches equilibrium in each of the void spaces. With traditional lay-up chemicals, the oxygen scavenger may become depleted easily (which is why the reserve usually is so high) and corrosion protection is quickly lost however, with VCI programs, there is always a volatile buffer available that maintains equilibrium and hence corrosion protection. 

D. Sikora. Hydrazine—a universal oxygen scavenger (hydrazyna— uniwersalny inhibitor korozji tlenowej w pluczkach wiertniczych). Nafta Gaz (Pol). 50(4) 161-168, April 1994. 

Autoxidation can lead to deterioration of food, drugs, cosmetics, or polymers, and inhibition of this reaction is therefore an important technical issue. The most important classes of autoxidation inhibitors are radical scavengers (phenols, sterically demanding amines [65, 66]), oxygen scavengers (e.g. ascorbic acid), UV-light absorbers, and chelators such as EDTA (to stabilize high oxidation states of metals and thereby suppress the metal-catalyzed conversion of peroxides to alkoxyl radicals) [67]. 

To be effective as autoxidation inhibitors radical scavengers must react quickly with peroxyl or alkyl radicals and lead thereby to the formation of unreactive products. Phenols substituted with electron-donating substituents have relatively low O-H bond dissociation enthalpies (Table 3.1 even lower than arene-bound isopropyl groups [68]), and yield, on hydrogen abstraction, stable phenoxyl radicals which no longer sustain the radical chain reaction. The phenols should not be too electron-rich, however, because this could lead to excessive air-sensitivity of the phenol, i.e. to rapid oxidation of the phenol via SET to oxygen (see next section). Scheme 3.17 shows a selection of radical scavengers which have proved suitable for inhibition of autoxidation processes (and radical-mediated polymerization). 

The hydrogen halide species behave as flame inhibitors by scavenging hydrogen, hydroxyl and oxygen radicals (Eqs. 11 and 12). 

Mekor . [Drew Ind. Div.] Volatile oxygen scavenger, metal passivator, corrosion inhibitor for boiler water treatment... 

OTHER COMMENTS used as a chemical intermediate in the preparation of higher bo-ranes, alkyl boranes, ethyl pentaborane, and various hydrides useful as jet and rocket fuels, catalysts, corrosion inhibitor fluxing agents, and oxygen scavengers. 

Formulations usually contain a combination of different anodic and cathodic inhibitors. Commonly used are ortho- and polyphosphates, phosphonates, tannins, lignins, benzoates, silicates, chromates, molybdates, nitrites, nitrates, zinc salts, aromatic azoles, carboxylic acids, amides, amines, soluble oils, and oxygen scavengers, such as hydrazine and sulfites [3, 46]. Some of these substances (e.g. silicates) are employed predominantly in synergy with other inhibitors, whereas in other cases the combination of inhibitors may have adverse effects (e.g. nitrites and organic amines or amides may form carcinogenic nitrosamines at elevated temperatures). 

To minimize the corrosion reactions, oxygen scavengers and corrosion inhibitors may be used as additives in solder-replacement adhesives. The percent changes in... 

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