Stainless steels acids

In the spht- or dual-pressure process, low to medium pressure gases (ca 0.3—0.6 MPa) containing nitrogen oxides are compressed to ca 1.1—1.5 MPa for efficient absorption in water to make nitric acid. Stainless steel is used for constmction in this corrosive environment and, because of the potential for... 

Weak Acid. Stainless steels (SS) have exceUent corrosion resistance to weak nitric acid and are the primary materials of constmction for a weak acid process. Low carbon stainless steels are preferred because of their resistance to corrosion at weld points. However, higher grade materials of constmction are required for certain sections of the weak acid process. These are limited to high temperature areas around the gau2e (ca 900°G) and to places in which contact with hot Hquid nitric acid is likely to be experienced (the cooler condenser and tail gas preheater). 

The development of improved control instrumentation [e.g., of cathode location (placements), etc.] and many years of proven AP applications in the field have made AP the preferred method of controlling corrosion of uncoated steel equipment handling hot, concentrated sulfuric acid, stainless steel in even hotter exposures, and even steel in nitric acid. 

The first-cycle raffinate wastes produced at the ICPP are the acid aluminum waste from various test reactor fuels, fluoride-bearing waste from zirconium-matrix fuel, a small amount of stainless steel sulfate waste from fuel from developmental reactors such as the Organic Moderated Reactor Experiment (OMRE), acid stainless steel nitrate waste from the electrolytic dissolution of Experimental Breeder Reactor-II (EBR-II) reactor fuel, and an acid waste from the recovery of uranium... 

Corrosion of Stainless Steels in Acids Stainless steels are iron-based alloys with chromium as the main alloying element. The most interesting alloys for technical applications are ferritic stainless steels, austentic stainless steels, and duplex stainless steels. The distinction between the stainless steels comes from their different crystallographic structures. Ferritic-martensitic stainless steels and martensitic stainless steels have less nickel and a higher carbon content and can be hardened by heat treatment. The corrosion behavior of these steels is mainly influenced by the formation of carbides, which generally increase the corrosion rate. 

Glass Polyvinyl chloride Styrene-ethylene/butylene-styrene block copolymer containers, beverages Resorcinol di (P-hydroxyethyl) ether containers, blow-molded Phenoxy resin containment, acids Stainless steel containment, gases Stainless steel... 

Polyethylene, ultrahigh m.w. Sodium bisulfide pultrusion Epoxy, bisphenol F pump, housings Polybutylene terephthalate pump/valve, housings Acetal homopolymer pumping, acids Stainless steel pumping, gases Stainless steel pumping, oils Stainless steel pumps... 

It is essential to ensure that a particular tanker is always used for transporting a particular chemical. If it is used to transport other chemicals, then the tanker should be thoroughly cleaned and dried to prevent contamination. The MOC of tanker outlet valves should be compatible with the transported material, e.g. MS-rabber lined for hydrochloric acid, stainless steel for nitric/acetic acid. Sampling valves should be fixed on all compartments of the tanker. 

The service hfe of exhaust systems has been greatly extended through the use of more corrosion-resistant materials [S]. These include stainless steels (types 409 and 430), alu-mininn coated steels, and aluminum-zinc coated steels [39]. The use of catal3iic converters presents some special problems because of the catalyzed oxidation reactions that take place in the exhaust gas stream. The converter itself must be highly corrosion-resistant because of its location near the exhaust manifold and the reaction to form acids such as sulfuric acid. Stainless steel is therefore widely used for the catalytic converter canister. More corrosion-resistant materials are also being used downstream frnm the converter. 

OSHA says that foam extinguishers with soldered brass shells and soda acid extinguishers with soldered brass shells must be retired from service. Soda acid (stainless steel shell) and cartridge operated water and/or antifreeze extinguishers are also obsolete. Also, any extinguisher which fails the hydrostatic testing requirements outlined in 1910.157(f)(10) must be retired. 

Formic acid production by the hydrolysis of methyl formate, such as the Leonard-Kemira process, is another modem process that requires zirconium. Formic acid is more highly ionized and therefore more corrosive than acetic acid. Stainless steels can be seriously attacked by intermediate... 

In the construction of tank wagons for the transport of chlorosulfonic acid, stainless steel was discovered to be the most suitable material. Studies were made of the effect of the reagent on mild steel, stainless steel and aluminium specimens, fully and half-immersed in the acid and when exposed to the acid vapour. When the samples were immersed, the stainless steel suffered almost no attack, whereas the other materials were appreciably corroded. Under the half-immersed conditions, the stainless steel was attacked above the liquid level, while in the vapour phase all the specimens were slightly attacked. ... 

Nickel is a moderately lustrous, silvery metal, and is extensively used in alloys (for example coinage, stainless steel) and for plating where a durable resistant surface is required. It is also used as an industrial catalyst, for example in the hydrogenation of unsaturated organic compounds. It is attacked by dilute aqueous acids but not by alkalis it combines readily with many non-metals on heating. 

Tellurium improves the machinability of copper and stainless steel, and its addition to lead decreases the corrosive action of sulfuric acid on lead and improves its strength and hardness. Tellurium is used as a basic ingredient in blasting caps, and is added to cast iron for chill control. Tellurium is used in ceramics. Bismuth telluride has been used in thermoelectric devices. 

Conversion of acetaldehyde is typically more than 90% and the selectivity to acetic acid is higher than 95%. Stainless steel must be used in constmcting the plant. This is an estabHshed process and most of the engineering is weU-understood. The problems that exist are related to more extensively automating control of the system, notably at start-up and shutdown, although even these matters have been largely solved. This route is the most rehable of acetic acid processes. 

Shipment, Stora.ge, ndPrices. Methyl vinyl ether is available in tank cars or cylinders, while the other vinyl ethers are available in tank cars, tank wagons, or dmms. Mild steel, stainless steel, and phenoHc-coated steel are suitable for shipment and storage. If protected from air, moisture, and acidic contamination, vinyl ethers are stable for years. United States bulk prices in 1991 for methyl vinyl ether, ethyl vinyl ether, and butyl vinyl ether were listed as about 5.78/kg, 6.28/kg, and 6.08/kg, respectively. 

The acryhc esters may be stored in mild or stainless steel, or aluminum. However, acryhc acid is corrosive to many metals and can be stored only in glass, stainless steel, alurninum, or polyethylene-lined equipment. Stainless steel types 316 and 304 are preferred materials for acryhc acid. 

Because of the highly corrosive nature of the nitric acid streams, adipic acid plants are constmcted of stainless steel, or titanium in the more corrosive areas, and thus have high investment costs. 

Pentaerythritol may be nitrated by a batch process at 15.25°C using concentrated nitric acid in a stainless steel vessel equipped with an agitator and cooling coils to keep the reaction temperature at 15—25°C. The PETN is precipitated in a jacketed diluter by adding sufficient water to the solution to reduce the acid concentration to about 30%. The crystals are vacuum filtered and washed with water followed by washes with water containing a small amount of sodium carbonate and then cold water. The water-wet PETN is dissolved in acetone containing a small amount of sodium carbonate at 50°C and reprecipitated with water the yield is about 95%. Impurities include pentaerythritol trinitrate, dipentaerythritol hexanitrate, and tripentaerythritol acetonitrate. Pentaerythritol tetranitrate is shipped wet in water—alcohol in packing similar to that used for primary explosives. 

In the batch process which finds occasional use, the steps used in the successive nitrations are similar and include acid mixing, addition of the oil, digesting (cooking) the reaction to completion, cooling and settling the mix, and separating the oil from the acid. The nitrators are made of stainless steel... 

Fluorosulfuric acid can be very corrosive. A study of the corrosive properties of fluorosulfuric acid during preparation and use showed carbon steel to be acceptable up to 40°C, stainless steel up to 80°C, and aluminum alloys up to 130°C (52). 

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