Industrial applications galvanic corrosion

This technique is referred to by a variety of terms, depending on the application immersion deposition, galvanic deposition (galvanic corrosion), conversion, cementation (in the metal recovery industry), and so on. 

The geometries discussed above are relevant to laboratory scale experimental cells. The geometries discussed below are more appropriate for situations encountered in industry or practical application involving galvanic corrosion, cathodic protection, or field corrosion probes. 

Thermal-sprayed galvanic coatings offer excellent corrosion and wear protection [73—75] and have been used in various industrial applications [76]. For the purpose of... 

CEMENT, PORTLAND. While in the fluid state, Portland cement causes etching of aluminum alloys as indicated in laboratory tests and in service applications. After the cement has set, no further corrosion occurs as a result of a protective film forming on the aluminum. Galvanic corrosion will develop If aluminum is coupled to dissimilar metals in cement or concrete to which chlorides have been added for high early strength. Aluminum alloys have been used for freight cars, hopper cars, and tote bins handling cement. Aluminum has also been used successfully for racks and pallets in the concrete block industry, molds and forms, and terrazzo divider strips. See also Ref (Dp. 129, (2) p. 161, (3) p. 228. 

Cadmium and zinc electroplating provides galvanic corrosion protection when coated on steel. Deposit thickness can vary between 5 and 25 p,m (0.2 and 1 mil), and typical applications for both coatings are found in Table 10. Cadmium is preferred for the protection of steel in marine environments, whereas zinc is preferred in industrial environments. Cadmium is also preferred for fastening hardware and connectors because its coefficient of friction is less than zinc. Cadmium is toxic and should not be used in parts that will have contact with food. Precautions for minimizing hydrogen embrittlement should be taken because cadmium plating is more susceptible to such embrittlement than any other plated metal. 

The ELMs could be apphed if the concentrations of precious metals in the wastewater range from 0.1 to 10,000 mg dm [90]. The apphcation of the ELMs based on non-Newtonian hquids and the Taylor-vortex column carry a lot of promise for industrial apphcations in the near future. Several commercial applications have been reported for ELM pertraction. Passivating is an operation commonly used in the galvanization industry to improve the resistance of metal parts to corrosion [87]. Metal parts are submerged into the passivating bath and become coated with Cr and/or Co to provide a protective layer against corrosion [87]. 

In addition to the well-known application of cathodic corrosion protection to underground pipelines, there has been an increased use for the internal protection of containers and pipes. Initially, galvanic anodes were used to this effect, like the ones currently used, for example, to protect the interiors of tankers and boilers. However, since these anodes are often subject to heavy inherent corrosion, especially with the highly aggressive media often found in the chemical industry, they have largely been replaced by external current systems with insoluble anode material. 

Because of these varying conditions a material that is resistant to atmospheric corrosion in one area might not be satisfactory in another area. For example, galvanized iron is perfectly suitable for application in a rural atmosphere but is not suitable when exposed to industrial atmospheres. 

Galfan finds application in a mild urban-industrial atmosphere and in a marine atmosphere. This latter application is particularly important because the corrosion rate slows after about 4 years, whereas conventional galvanized steel should show rust in 5 years. This slower rate of corrosion is evidence that the zinc-5% aluminum coatings provide full cathodic protection to cut edges over a longer period of time. 

---