Galvanized basis material

Effluent Limitations and Performance Standards of the Galvanized Basis Material Subcategory... 

Table 7.25 shows the effluent limitations of the galvanized basis material subcategory that represents the degree of effluent reduction attainable by the application of the BPT currently available. Table 7.26 shows the effluent limitations of the galvanized basis material subcategory that represents the degree of effluent reduction attainable by the application of the BAT economically achievable. 

The Effluent Limitations of the Galvanized Basis Material Subcategory that Represent the Degree of Effluent Reduction Attainable by the Application of the BPT Currently Available... 

Table 7.27 lists the new source performance standards of the galvanized basis material subcategory that establish the quantity or quality of pollutants or pollutant properties. Table 7.28 lists the pretreatment standards for existing sources of the galvanized basis material subcategory effluents. Table 7.29 lists the pretreatment standards for new sources of the galvanized basis material subcategory effluents. 

The New Source Performance Standards (NSPS) of the Galvanized Basis Material Subcategory that Establish the Quantity or Quality of Pollutants or Pollutant Properties... 

Galvanized basis material means zinc coated steel, galvanized brass, and other copper base strip that is processed in coil coating. 

The basic objective of the conversion coating process is to provide a corrosion-resistant film that is integrally bonded chemically and physically to the base metal and that provides a smooth and chemically inert surface for subsequent application of a variety of paint films. The conversion coating processes effectively render the surface of the basis material electrically neutral and immune to galvanic corrosion. Conversion coating on basis material coils does not involve the use of applied electric current to coat the basis material. The coating mechanisms are chemical reactions that occur between solution and basis material.1-4... 

Wastewater generation occurs for each basis material (steel, galvanized and aluminum) and for each functional operation (cleaning, conversion coating, and painting). The wastewater generated by the three functional operations may be handled in one of the following ways ... 

Consideration will also be given to attack arising from contact with solids such as refractories, and with molten materials such as salts, glasses, and lower-melting-point metals and alloys. On a fundamental basis, the distinction between some of these latter reactions and normal-temperature aqueous corrosion is not always clear, since galvanic effects may be of significance in both cases, but for practical purposes a distinction can be made on the basis of the temperature involved. 

Other questions can be answered by electrochemical testing. By measuring the behavior of the different materials in a complex structure, it is possible to determine if the corrosion rate of certain components of a structure will be enhanced by galvanic interactions. The basis for making this assessment was given in Sect. 1.3 of this volume. 

Express on this basis if the galvanic series is suitable for indication of galvanic corrosion rates. Which property determines the galvanic current density in Table 7.3 Explain the data in Table 7.3 by means of schematic polarization curves of the materials in question. 

On a weight basis in many locations, dust is the primary air contaminant. When in contact with metallic surfaces and combined with moisture, dust can promote corrosion by forming galvanic or differential cells that, because of their hygroscopic nature, form an electrolyte on the surface. Suspended particles of carbon and carbon compoimds, metal oxides, sulfuric acid, ammonium sulfate, sodium chloride, and other salts will be foimd in industrial atmospheres. It is these materials, when combined with moisture, that initiate corrosion. 

Corrosion sodium chloride solution is aroimd 0.23 V (SCE), which compares with 0.38 V for type 304 stainless steel. This puts titanium-nickel on the noble or protected side of steiinless steel in the galvanic series. A passive oxide/nitride surface film is the basis of the corrosion resistance of titanium-nickel alloys, similar to stainless steels. Specific environments can cause the passive film to break down, thus subjecting the base material to attack. A summary of titanium-nickel reactions in various environments follows (Ref 28). 

The standard emf and galvanic series are rankings of metallic materials on the basis of their tendency to corrode when coupled to other metals. 

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