Copper corrosion characteristics

Generally, the process of manufacture has no appreciable effect on the corrosion characteristics of steel. Slight variations in composition that inevitably occur from batch to batch in steels of the same quality have little effect with the exception of copper, the effect of which is discussed more fully in Section 3.2. 

Even though the exposure test in practical sites is stiU very important and useful, we StiU need laboratory tests. It would be very useful to accelerate the corrosion characteristics and to evaluate the results in a relatively short time. This category has some laboratory tests filling the gap between the exposure test and very fundamental electrochemical tests. To name a few, we can mention the salt spray test, a CASS (Copper accelerated acetic acid salt spray) test, and a combined cycle test [4],... 

A less but still complicated situation is found for actively corroding alloys which are not covered by passive layers, particularly in acidic electrolytes. In many cases, the very different corrosion characteristics of the alloying elements lead to preferential dissolution of one metal component. The preferential oxidation or dissolution of the zinc of brasses and the related accumulation of copper at the surface is a technologically important example of dealloying of a metal surface. In this case zinc is much more... 

Water environments can also have a variety of compositions and corrosion characteristics. Freshwater normally contains dissolved oxygen as well as minerals, several of which account for hardness. Seawater contains approximately 3.5% salt (predominantly sodium chloride), as well as some minerals and organic matter. Seawater is generally more corrosive than freshwater, frequently producing pitting and crevice corrosion. Cast iron, steel, aluminum, copper, brass, and some stainless steels are generally suitable for freshwater use, whereas titanium, brass, some bronzes, copper-nickel alloys, and nickel-chromium-molybdenum alloys are highly corrosion resistant in seawater. 

Performance can be illustrated for example by the time necessary for deaeration or de-emulsification of oils, anti-rust properties, copper strip corrosion test, the flash point in closed or open cup, the cloud and pour points, the foaming characteristics, etc. 

Glass-lined reactor systems ate used occasionally for halogenated resins to prevent corrosion of the reactor components. Copper and brass fitting should be avoided due to the significant induence on resin cute characteristics. 

Corrosion. Copper and selected copper aHoys perform admirably in many hostile environments. Copper aHoys with the appropriate corrosion resistance characteristics are recommended for atmospheric exposure (architectural and builder s hardware), for use in fresh water supply (plumbing lines and fittings), in marine appHcations (desalination equipment and biofouling avoidance), for industrial and chemical plant equipment (heat exchangers and condensers), and for electrical/electronic appHcations (coimectors and semiconductor package lead-frames) (30) (see Packaging). 

In safety applications, the corrosion resistance of the duct materials deserv es special consideration. Since material costs generally increase along with corrosion resistance, the selection of material must be determined by the desired life span in the anticipated environment this environment is a function of the characteristics of the chemical being processed and the operating conditions of the reactor. For maximum resistance to moisture or corrosive gases, stainless steel and copper are used where their cost can be justified. Aluminum sheet is used where lighter veight and superior resistance to moisture are needed. 

This is the exchanger where heat flows from the room return or mixed air to cold refrigerant or to chilled water. It is an arrangement of finned tubes normally of aluminum fins on copper tubes, but copper fins can be specified for corrosive atmosphere. Performance characteristics are controlled by fin and tube spacing. If the room rh is high, dehumidification may be brought into use by operating the coil or one of a number of parallel coils at a low temperature. If the room s sensible heat load is low reheat must be allowed to operate at the same time. 

Silver-copper-palladium alloys with liquidus temperatures of 800-1 000°C have very low vapour pressures combined with good wetting and flow characteristics and are widely employed in vacuum work. They exhibit a lower tendency to stress corrosion than silver-copper, and do not form brittle alloys with other metals. 

For long lengths of anode it is sometimes necessary to extrude one material over another to improve a particular characteristic. Thus titanium may be extruded over a copper rod to improve the longitudinal conductivity and current attenuation characteristics of the former lead alloys may be treated similarly to compensate for their poor mechanical properties. It should he noted that these anodes have the disadvantage that, should the core metal be exposed to the electrolyte by damage to the surrounding metal, rapid corrosion of the former will occur. 

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