Corrosion of pharmaceutical equipment

This discussion provides for a fundamental understanding of corrosion and corrosion processes. It also offers an overview of both metallic and non-metallic materials utilized in the construction of pharmaceutical equipment and some of the special considerations in their application. Suppliers of materials and fabrication services are valuable resources of information and should be included in the design process. Because corrosion processes are often complex, the services of corrosion engineering professionals should be considered in the original design or performance analysis activities as part of an in-house team, or on a consulting basis. 

Materials required in the fabrication of equipment and associated systems dedicated to the production of pharmaceutical products should be capable of withstanding the temperature, pressure, and chemical corrosiveness of the product to ensure its purity and integrity. They also must meet a high degree of cleanliness to convey sterile and non-sterile products or solutions, particularly when it applies to their contact surfaces. Contact surfaces are all surfaces exposed to the product or from which liquids may drain, drop, or be drawn into the product, and solution contact surfaces are the interior surfaces of the circuit used exclusively for supply and recirculation of cleaning and/or sanitizing solutions. ... 

In the manifold types of production processes in industry, waters of very different properties are required, depending on the type of plants and on the technological processes. For example, the foodstuff industry requires hy-gienically safe water, production of pharmaceuticals and fine chemicals requires distilled water, for other industries (metallurgical, engineering, etc.) simply treated or even untreated surface water is sufficient. Unsuitable quality of industrial water can cause a deterioration in the quality of products, reduced production capacity and equipment corrosion. Except for some specific requirements for the quality of water for the different industrial sectors, some requirements are common to the majority of operations [1-8] ... 

Materials of Construction. In a great many cases, steel is suitable for the construction of alkylating equipment, even in the presence of the strong acid catalysts, as their corrosive effect is greatly lessened by the formation of esters as catalytic intermediate products. In the petroleum industry, sulfuric acid and hydrogen fluoride are employed on a very large scale as alkylation catalysts however, these must be substantially anhydrous to be effective so steel equipment is satisfactory. Where conditions are not anhydrous, lead-lined, Monel-lined, or enamel-lined equipment is satisfactory. In a few cases, copper or tinned copper is still used, as in the manufacture of pharmaceutical and photographic products, to lessen contamination with metals. 

Throughout history, metals have had a decisive effect on human civilization, and they largely condition the way we live today. Electric power, combustion engines, ships, cars, railways, airplanes, production of fertilizers and pharmaceuticals, precision tools, machines, high rise buildings, sanitary systems, home appliances and even computers would not exist without metals. Corrosion and wear limit the useful lifetime of this equipment, reduce their efficiency and often affect their safety. Corrosion control and surface technology are therefore of crucial importance for our technology-based society. 

Zinc is also used extensively to galvanize other metals such as iron to prevent corrosion. Zinc oxide is a unique and very useful material for modern civilization. It is widely used in the manufacture of paints, rubber products, cosmetics, pharmaceuticals, floor coverings, plastics, printing inks, soap, storage batteries, textiles, electrical equipment, and other products. Lithopone, a mixture of zinc sulfide and barium sulfate, is an important pigment. 

Titanium is being employed in the bleaching industry where the good corrosion resistance of the material makes it particularly suitable for equipment in both textile and paper pulp bleaching processes. In the dye-stuffs industry, the inertness of titanium eliminates any products of corrosion which might cause discoloration of the products. A similar situation can also exist in areas like the plastics, pharmaceuticals, and food-stuffs industries. 

The design of equipment for use in controlled environment areas follows similar principles, whether for general injectable manufacturing or for the manufacturer of sterile ophthalmic pharmaceuticals. All tanks, valves, pumps, and piping must be of the best available grade of corrosion-resistant stainless steel. In general, stainless steel type 304 or 316 is preferable. 

For pharmaceutical applications in particular, the rate of corrosion must be considered not only for the effect on equipment, but where the lost metal has gone. Product contamination can be of concern for other products as well, and when this is an issue, the selection of more corrosion-resistant materials is of utmost importance. 

Glassware and glass-lined equipment also offer excellent resistance to corrosion, similar to that of ceramic materials. In addition to the advantages of corrosion resistance, it also affords a very cleanable surface. Glass-lined vessels are used in the pharmaceutical industry for reactors, mixers, storage tanks, transfer piping, and high-purity water systems. 

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