Fretting Corrosion Mitigation

In reference to Fig. 7.39, one could be tempted to say that it is easy to prevent mitigation of SCC. Simply eliminate the stress, isolate the 

Change of material A total or even partial change of material (e.g., safe-ending of heat-exchanger tubes) is a common approach. For complete reliability, use of a superior crack-resistant material is often the most cost-economical approach. 

Change of environment The removal of chlorides, caustic, or other major cracking-type species is an effective solution where possible. However, much less drastic changes are often effective as 

Electrochemical techniques Cathodic protection has been found effective against anodic SCC. Lead-tin solders and nickel plating have been used to protect stainless steel tube ends against SCC by water. This technique must be carefully controlled to be effective. Austenitic stainless steel has been known to suffer chloride SCC while simultaneously causing galvanic corrosion of steel components. 

The following are general recommendations to avoid the initiation of see due to the formation of corrosion cells in service. 

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The notion of a gas-tight seal as the product of a proper press-fit is crucial to connection reliability. If an electrical contact is to be rehable, the interface between the two mating surfaces must remain chemically and mechanically stable. The gas-tight, smeared, metal-to-metal contact attained during the press-fit operation mitigates oxidation of either contact (FTH barrel or press-fit pin) and prevents fretting corrosion, which is a common failure mechanism for mechanically mated contacts, especially those subjected to vibration. Press-fit interconnection is considered at least as rehable as a soldered connection and there is no solder joint to degrade or crack with time. 

Any action in mitigating flow maldistribution must be preceded by an identification of possible reasons that may cause the performance deterioration and/or may affect mechanical characteristics of the heat exchanger. The possible reasons that affect the performance are [131,147] (1) deterioration in the heat exchanger effectiveness and pressure drop characteristics, (2) fluid freezing, as in viscous flow coolers, (3) fluid deterioration, (4) enhanced fouling, and (5) mechanical and tube vibration problems (flow-induced vibrations as a consequence of flow instabilities, wear, fretting, erosion, corrosion, and mechanical failure). 

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