Cooling water, corrosion inhibitors sulfuric acid

Obviously when we deliberately add sulfuric acid to cooling water, we reduce alkalinity and also depress pH. This increases corrosivity of the circulating water, which is saturated with dissolved oxygen, contacts many dissimilar metals, and is elevated in temperature. In the process of acidification to prevent scale deposition so heat transfer equipment will function efficiently, we knowingly build in added corrosion factors and increase corrosion control difficulty. Now we need to find corrosion inhibitor combinations which will be practical for use in industrial systems can be tolerated from the viewpoints of toxicity and pollution controls and will effectively protect these multimetal circuits during their normal service life of 20 to 30 years. 

Earlier the standard industrial approach to prevention of calcium carbonate scaling by addition of sulfuric acid was described. Objectives were to reduce bicarbonate alkalinity, convert calcium carbonate to calcium sulfate, and regulate sulfate concentration by bleedoff. Corrosion inhibitors were added to protect system metals. A new approach to industrial cooling system treatment does not require addition of sulfuric acid. It involves application of phosphonate seques-trants, dispersants and special corrosion inhibitors, and provides deposit control equal to that obtainable when using sulfuric acid. Availability of phosphonate sequestrants makes possible combination scale control and corrosion inhibitors that can be used without the necessity of reducing cooling water alkalinity by acid feed. 

Triamylamlne is a water-white ta light yellow, stable liquid which is strongly basic in reaction. It is soluble in ethyl alcohol, ethyl ether, ethyl acetate, acetone, aromotic and aliphatic hydrocarbons, fixed oils, mineral oil, oleic and stearic acids, and in hot paraffin and carnauba waxes, the latter two solidifying when cooled. It is insoluble in water and methyl alcohol. It is on excellent corrosion inhibitor of steel in a 0.13% solution in rtormal sulfuric acid. It is used In the manufacture of emulsifying agents, dyestuffs, and insecticides. 

The sulfuric acid used to dry the chlorine is also sometimes a source of ammonia compounds. Finally, the plant utilities are likely sources. Plant water that has not been thoroughly purified has many opportunities to enter the process. Examples of these opportunities are the use of impure water to prepare treatment chemical solutions, flushing water on rotating machinery seals, water recycle from waste-minimization systems, and direct-contact cooling water. Steam and its condensate are also potential sources. The culprits here usually are the amines used as corrosion inhibitors in the steam system (Section 12.3.2). 

Compatibility Corrosion inhibitors can undergo reactions with components of the environment. Amines react with HjS. Unsaturated fatty acids and derivatives thereof (imidazolines) are subject to vulcanization in the presence of elemental sulfur or oxygen in combination with HjS. Polyfunctional acids react with polyfunctional amines to form gels or solids. Such considerations are important, since production or process streams are often treated with more than one chemical (oil and gas production processing, transport and refining, cooling water circuits— the examples are endless). 

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