Copper galvanic corrosion with

Vanadium is resistant to attack by hydrochloric or dilute sulfuric acid and to alkali solutions. It is also quite resistant to corrosion by seawater but is reactive toward nitric, hydrofluoric, or concentrated sulfuric acids. Galvanic corrosion tests mn in simulated seawater indicate that vanadium is anodic with respect to stainless steel and copper but cathodic to aluminum and magnesium. Vanadium exhibits corrosion resistance to Hquid metals, eg, bismuth and low oxygen sodium. 

Aluminum is not embrittled by low temperatures and is not subject to external corrosion when exposed to normal atmospheres. At 200°C (400°F) its strength is less than half that at room temperature. It is attacked by alkahes, by traces of copper, nickel, mercuiy, and other heaw-metal ions, and by prolonged contact with wet insiilation. It suffers from galvanic corrosion when coupled to copper, nickel, or lead-... 

Area effects in galvanic corrosion are very important. An unfavorable area ratio is a large cathode and a small anode. Corrosion of the anode may be 100 to 1,000 times greater than if the two areas were the same. This is the reason why stainless steels are susceptible to rapid pitting in some environments. Steel rivets in a copper plate will corrode much more severely than a steel plate with copper rivets. 

Similarly, graphitically corroded cast iron (see Chap. 17) can assume a potential approximately equivalent to graphite, thus inducing galvanic corrosion of components of steel, uncorroded cast iron, and copper-based alloys. Hence, special precautions must be exercised when dealing with graphitically corroded pump impellers and pump casings (see Cautions in Chap. 17). 

In applying electrolytic protection, galvanized tubes can be installed downstream from copper components in water boilers without danger of Cu " -induced pitting corrosion. The protection process extends the application range for galvanized tubes with respect to water parameters, temperature and material quality beyond that in the technical regulations [16, 17]. 

Heat exchangers that utilize copper coils are potential candidates for galvanic corrosion due to dissolved copper salts interacting with the galvanized steel shell. This problem can be avoided by nickel plating the coils. The coils then can be separated from direct contact with the vessel via insulation. Also, it is preferable to conduct the water on the tube side of heat exchangers. 

Solar water heating declined in Southern California in the 1920s due to the development of natural gas, but it continued in Florida where natural gas was very expensive. In 1941 more than half Miami s population had solar water heaters, and more than 80 percent of new homes built then were equipped with solar water heaters. By the end of the 1950s in Florida, solar water heating was displaced by electricity as the price dropped and the storage tanks of solar water heaters failed because of galvanic corrosion from connecting steel tanks to copper collectors. 

Galvanic corrosion is the enhanced corrosion of one metal by contact with a more noble metal. The two metals require only being in electrical contact with each other and exposing to the same electrolyte environment. By virtue of the potential difference that exists between the two metals, a current flows between them, as in the case of copper and zinc in a Daniell cell. This current dissolves the more reactive metal (zinc in this case), simultaneously reducing the corrosion rate of the less reactive metal. This principle is exploited in the cathodic protection (Section 53.7.2) of steel structures by the sacrificial loss of aluminum or zinc anodes. 

There is an accelerating trend away from the use of lead-containing solders in contact with potable water. The effects of galvanic corrosion of one of the substitute alloys (Sn3%Ag) in contact with a number of other metals including copper have therefore been studied . The corrosion of tin/Iead alloys in different electrolytes including nitrates, nitric and acetic acids, and citric acid over the pH range 2-6 were reported. The specific alloy Pb/15%Sn was studied in contact with aqueous solutions in the pH range... 

Some combinations of lead with other metals such as iron and copper are prone to galvanic corrosion. 

Dissimilar metals. Galvanic corrosion occurs when two metals with different electrochemical potentials are in contact in the same solution [Figures 6.7 and 6.8]. In both cases, the corrosion of iron (steel) is exothermic and the cathodic reaction is controlling the corrosion rate. The more noble metal, copper increases the corrosion through cathodic reaction of hydrogen ion reduction and hydrogen evolution A passive oxide film on stainless steel for example can accelerate hydrogen reduction reaction. 

Thus, if dissimilar pipes are butt-welded with the electrolyte flowing through them, the most severe corrosion will occur adjacent to the weld on the active metal. The current of the galvanic cell takes the path of least resistance and this affects corrosion in that current does not readily flow around corners. In soft water, the critical distance between copper and iron may be 5 mm in seawater it may be several decimeters. The critical distance is greater the larger the potential difference between anode and cathode. Then, the geometry of the circuit affects galvanic corrosion and this is observed in the case of stray current corrosion.7 (Baboian)5... 

The new dress-cap substrate material should be either fiber-reinforced plastic (FRP) or Type 316 stainless steel. Being a nonmetallic insulator, FRP would eliminate any possibility of galvanic corrosion. Type 316 stainless steel demonstrates good passivity in urban atmospheres and has been successfully used in contact with copper.1... 

A porous or cracked mill scale can expose the steel substrate underneath the rinse solution, Table 7.18. The mill scale will then act as a cathode, and the exposed area, which will be an anode, will undergo galvanic corrosion. Due to the large-area cathode compared with the small-area anode (exposed through the cracks in the mill scale), the corrosion rates will be quite high. The presence of copper within the mill scale can increase the cathodic reduction rate, thus accelerating further the corrosion of steel in the exposed regions. 

As mentioned above, the environment has a significant effect on whether or not galvanic corrosion will be a problem. For example, carbon steel will corrode rapidly if equal or larger areas of Monel 400 are coupled with it in seawater. Conversely, carbon steel is compatible with Monel 400 in concentrated caustic solutions. Even freshwater can be sufficiently different from seawater couples incompatible in seawater work well in freshwater. For example, copper-steel and aluminum-steet couples are satisfactory for handling... 

Galvanic corrosion tends to occur when two metals with different electrochemical potentials are electrically connected and exposed in an electrolyte. As a result, the less noble metal will suffer from accelerated corrosion [58]. When excess copper is polished away by copper CMP, copper and barrier metal are exposed to the CMP slurry simultaneously. Copper and barrier metal have different electrochemical potentials and thus trigger galvanic corrosion at the interface between copper and barrier metal at a certain kind of slurry composition. In this galvanic corrosion, electrons are transferred from titanium anode to copper cathode. During overpolishing of the patterned wafer, titanium near the copper structure is recessed owing to dissolution (Ti Ti -I- 2e ) and Cu " ions are preferentially deposited onto... 

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