Corrosion ships

The steel hull of oceangoing ships offers strength, reliability, and durability, but steel is susceptible to corrosion. Ships such as this one in St. John Harbour, New Brunswick, Canada, often show the telltale sign of corrosion, which is rust. 

As stated above the life of a ship will be determined by corrosion and fatigue damage. The assessment of corrosion and fatigue damage is discussed below. 

It is possible that much of the inspection in future years will be focused on areas identified from databases which collate corrosion and damage history in similar ships. The validity of any conclusions derived from assessment programmes or databases can only be accepted if the quality of the original product is known. This would suggest that the NDE inspection programmes applied by some yards will have to be expanded. 

As an example of the effect that corrosion can have on connnercial industries, consider the corrosive effects of salt water on a seagoing vessel. Corrosion can drastically affect a ship s perfonnance and fiiel consumption over a period of time. As the hull of a steel boat becomes corroded and fouled by marine growths, the... 

Figure A3.10.2 The influence of corrosion (C) and marine fouling (F) on the perfonnance of a steel ship dry docked amuially for cleaning and painting [5].

Titanium has potential use in desalination plants for converting sea water into fresh water. The metal has excellent resistance to sea water and is used for propeller shafts, rigging, and other parts of ships exposed to salt water. A titanium anode coated with platinum has been used to provide cathodic protection from corrosion by salt water. 

Furfuryl alcohol is shipped in bulk or dmms. Although not corrosive to metals, it is a powerful solvent and penetrant containers, tanks, lines, and valves need to be in good condition to avoid potential leakage. Furfuryl alcohol can be stored in containers lined with baked phenoHc resin coatings however, it should not be put in containers that are coated with lacquers, varnishes, or epoxy resins because it is an excellent solvent for many such coatings. 

Acetic acid, fp 16.635°C ((1), bp 117.87°C at 101.3 kPa (2), is a clear, colorless Hquid. Water is the chief impurity in acetic acid although other materials such as acetaldehyde, acetic anhydride, formic acid, biacetyl, methyl acetate, ethyl acetoacetate, iron, and mercury are also sometimes found. Water significantly lowers the freezing point of glacial acetic acid as do acetic anhydride and methyl acetate (3). The presence of acetaldehyde [75-07-0] or formic acid [64-18-6] is commonly revealed by permanganate tests biacetyl [431-03-8] and iron are indicated by color. Ethyl acetoacetate [141-97-9] may cause slight color in acetic acid and is often mistaken for formic acid because it reduces mercuric chloride to calomel. Traces of mercury provoke catastrophic corrosion of aluminum metal, often employed in shipping the acid. 

According to the U.S. DOT regulations, acetic acid is a corrosive material (71). It may be shipped in metal or plastic packaging when no more than... 

Little is known of the market for acetyl chloride. The production and sales are beUeved to be small, but may have potential for very large scale-up. The total U.S. market may amount to only 500 t annually. Acetyl chloride must be shipped in polyethylene-lined dmms having capacities of only 220 L it must be labeled as a corrosive substance. Acetyl chloride generated captively from purchased raw materials probably has a unit value of no more than 0.92—0.95/kg. Shipping costs and other factors set the price at about 3/kg for the commercial trade. 

Fluoroboric acid and some fluoroborate solutions are shipped as corrosive material, generally in polyethylene-lined steel pads and dmms or in rigid nonretumable polyethylene containers. Acid spills should be neutralized with lime or soda ash. 

Cobalt difluoride, used primarily for the manufacture of cobalt trifluoride, CoF, is available from Advance Research Chemicals, Inc., Aldrich Chemicals, and PCR in the United States, Fluorochem in the UK, and Schuhardt in Germany. The 1993 price varied from 60 to 200/kg depending on the quantity and the price of cobalt metal. C0F2 is shipped as a corrosive and toxic material in DOT-approved containers. 

The ACGIH adopted TLV/TWA for 1992—1993 for fluorides as F is TWA 2.5 mg/m, and for cobalt as Co metal dust TWA 0.05 mg/m. Dust masks should be used while handling both the cobalt fluorides and all other cobalt compounds. CoF is shipped as an oxidizer and a corrosive material. 

Specifications, Shipping, and Analysis. Hydrogen fluoride is shipped in bulk in tank cars (specification 112S400W) and tank tmcks (specification MC312). A small volume of overseas business is shipped in ISO tanks. Bulk shipments are made of anhydrous HF as well as 70% aqueous solutions. A small amount of aqueous solution may be shipped as 50%. Cars and tmcks used for anhydrous HF transport are of carbon steel constmction. It is possible to ship 70% aqueous in steel from a corrosion standpoint however, mbber lining is commonly used to eliminate iron pickup, which is detrimental to product quaUty in a number of appHcations. Hydrogen fluoride of less than 60% strength must always be shipped in lined containers. 

Molybdenum hexafluoride is classified as a corrosive and poison gas. It is stored and shipped in steel, stainless steel, or Monel cylinders approved by DOT. Electronic and semiconductor industries prefer the cylinders equipped with valves which have Compressed Gas Association (CGA) 330 outlets. 

Titanium trifluoride can be stored in tightly closed polyethylene containers for several years. Shipping regulations classify the material as a corrosive sohd and it should be handled in a fully ventilated area or in a chemical hood. The ACGIH adopted toxicity values (1992—1993) for TiF is as TWA for fluorides as F 2.5 mg/m. ... 

Tungsten hexafluoride is shipped as a Hquid under its own vapor pressure in nickel or steel cylinders in quantities of 45 kilograms per cylinder or less however, it has been shown that the purity of WF packaged in steel cylinders can degrade over time (21). It is classified as a corrosive Hquid by the... 

In unalloyed steel containers formamide discolors slowly during shipment and storage. Both copper and brass are also subject to corrosion, particularly in the presence of water. Lead is less readily attacked. Aluminum and stainless steel are resistant to attack by formamide and should be used for shipping and storage containers where the color of the product is important or when metallic impurities must be minimized. Formamide attacks natural mbber but not neoprene. As a result of the solvent action of formamide, most protective paints and finishes are unsatisfactory when in contact with formamide. Therefore, formamide is best shipped in containers made of stainless steel or in dmms made of, or coated with, polyethylene. Formamide supphed by BASF is packed in Lupolen dmms (230 kg) or Lupolen canisters (60 kg) both in continental Europe and overseas. 

The Department of Transportation classifies HCl as a corrosive material and requires that it be transported in DOT-approved deHvery vessels. Tank cars must conform to 103B, 103B-W, or DOT 111A60W5 specifications. Tank trailers must conform to DOT MC-310, MC-311, MC-312, or DOT-412 specifications with display of a corrosive placard on both sides, front, and rear of the tank. The United Nations identification number for muriatic acid is UN1789, which must appear on aH shipping papers and placards. 

In handling, shipping, and storing DRI, care should be taken to avoid oxidation. Millions of tons of DRI in pehet and lump form have been shipped by barge, ocean vessel, tmck, and rad. The key to avoiding oxidation is simply to keep the material cool and dry. The chemical reactions involved have been well documented. In general, oxidation of DRI takes place in two forms reoxidation and corrosion (2). 

In comparison, HBI is almost twice as dense as DRI, and thus does not absorb as much water and is much more resistant to reoxidation and corrosion. Several methods of passivating DRI to make it more resistant to reoxidation and corrosion have been developed, but none has been as effective as hot briquetting. Guidelines for offshore shipping of peUet/lump DRI and HBI have been prepared by the International Maritime Organization. 

Commercial-grade nitroparaftins are shipped and stored ia ordinary carbon steel. However, wet nitroparaftins containing more than 0.1—0.2% water may become discolored when stored ia steel for long periods, even though corrosion is not excessive. Aluminum and stainless steel are completely resistant to corrosion by wet nitroparaftins. Storage ia contact with lead (qv), copper, or alloys containing these metals should be avoided. Polymeric materials for gaskets, hoses, and connections should be tested for thek suitabiHty before exposure to nitroparaftins. 

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