Design for corrosion resistance

The life of equipment subjected to corrosive environments can be increased by proper attention to design details. Equipment should be designed to drain freely and completely. The internal surfaces should be smooth and free from crevasses where corrosion products and other solids can accumulate. Butt joints should be used in preference to lap joints. The use of dissimilar metals in contact should be avoided, or care taken to ensure that they are effectively insulated to avoid galvanic corrosion. Fluid velocities and turbulence should be high enough to avoid the deposition of solids, but not so high as to cause erosion-corrosion. 

Baines, D. (1984) Chem. Engr., London No. 161 (July) 24. Glass reinforced plastics in the process industries. Bendall, K. and Guha, P. (1990) Process Industry Journal (Mar.) 31. Balancing the cost of corrosion resistance. 

(1970) Brittle Fracture of Steel Structures (Butterworths). 

and Wright, D. C. (1980) Use of Polymers in Chemical Plant Construction (Applied Science). Champion, F. A. (1967) Corrosion Testing Procedures 3rd edn (Chapman Hall). 

(1970) Chem. Engr. London No. 242 (Oct.) 312. Carbon Steels for the construction of chemical and allied plant. 

) (1971) Handbook of Corrosion Testing and Evaluation (Wiley). 

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Design for corrosion resistance may be almost exclusively for appearance when favorable appearance is an economic advantage. Stainless steel and aluminum are frequently used for architectural applications and in food service largely for appearance. They also are used for trim on automobiles for the same reason. 

FIG. 5—Critical areas and use of galvanized steel on automobile designed for corrosion resistance (courtesy of L. L. Peipho, General Motors Corporation, Milford Proving Grounds). 

Some particular requirements and typical selection considerations are presented in Table 11.2. The material selection process is also influenced by the fact that the materials are either considered for the construction of a new system, or for the modification or repairs in an existing facility. For the construction of new equipment, the selection procedure should begin as soon as possible and definitively much before the design is finalized since the optimum design for corrosion resistance may greatly affect how the system will be assembled or constructed. 

The basic faaors that most influence design for corrosion resistance are summarized in Table 1. Each factor plays a unique yet not always unrelated role with... 

The uniform structure of Austenite (fee, with the carbides in solution) is the structure desired for corrosion resistance, and it is these grades that are widely used in the chemical industry. The composition of the main grades of austenitic steels, and the US, and equivalent UK designations are shown in Table 7.7. Their properties are discussed below. 

Reduce junking frequency. Design for corrosion and wear resistance easy maintainability. Discourage frequent styling changes simply in interest of increasing marketing appeal. 

Terephthalic Acid from Toluene. Both carbon monoxide and methanol can react with toluene to yield intermediates that can be oxidized to terephthalic acid. In work conducted mainly by Mitsubishi Gas Chemical Company (62,63), toluene reacts with carbon monoxide and molar excesses of HF and BF3 to yield a jtanz-tolualdehyde—HF—BF3 complex. Decomposition of this complex under carefully controlled conditions recovers HF and BF3 for recycle and ra-tolualdehyde, which can be oxidized in place of para-xyiene to yield terephthalic acid. One drawback of the process is the energy-intensive, and therefore high cost, decomplexing step. The need for corrosion-resistant materials for construction and the need for extra design features to handle the relatively hazardous HF and BF3 also add to the cost. This process can be advantageous where toluene is available and xylenes are in short supply. 

This specification provides guidelines for the design and fabrication, of vessels that are to be membrane-lined, and to receive a chemical-resistant masonry lining for corrosion resistance. 

If you are designing a corrosion-resistant tank of rolled (annealed) Hastelloy alloy C, the tensile strength needed for your calculations is 896 MN/m, which is... 

R. Bandy and D. Van Royan, Properties of Nitrogen-Containing Stainless Alloy Designed for High Resistance to Pitting, Corrosion, Vol 41, 1985, p 228-233... 

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