Oxidation debris

Fretting corrosion (36,37) can lead to high contact resistance of base metal contacts, such as tin plate in electronic connectors. Small cycHcal displacements of the connector halves occur because of external vibration or differential thermal expansion and contraction of the mating contacts. The wear debris that is formed remains in the contact zone. The accumulation of oxide debris in the contact region leads to increased contact resistance. Solutions to this problem are stmctures that do not permit movement of contact surfaces with respect to one another, the use of gold as a contact finish, and the appHcation of thick coatings of contact lubricants and greases, which reduce the rate of wear and restrict access of air to the contact surfaces. 

The relative humidity of the atmosphere has a large effect on the magnitude of wear", but in a direction opposite to that which is encountered in normal corrosion problems. The increasing wear towards lower humidities is accompanied by severe pitting of the surfaces and, under extremely dry conditions, the oxide debris produced from steel surfaces is jet black. 

Oils may act in two ways they provide a measure of boundary lubrication and they may exclude oxygen from the rubbing zone. However, their effectiveness is not as great as with unidirectional sliding, since there is usually sufficient oxygen present in most cases to allow oxide debris to be generated, and this tends to displace any lubricant film that was initially present between the surfaces. 

The stoichiometric relationship for hydrazine with oxygen is 1 1, but it is always added at between two and four times theoretical to ensure that the reaction proceeds to completion. Even so, it may be some time after startup (often one to two weeks) before hydrazine appears in the BW as a reserve. This probably is due to the hydrazine reducing all existing ferric oxide in the system first. During this time, the color of the oxide debris and surface oxides change from reddish brown to black (passivation). 

Once a filmer program starts, feeding of amine must be continuous because with the gradual removal of old iron oxide debris, the clean metal surface is subject to rapid corrosion should the continuous film cease to be maintained. 

Evidently, fretting is worse in air than in an inert atmosphere.25 There is less damage in a humid atmosphere than in dry air since humidity can have a lubricant action, and the hydrated oxides are less hard than the dry oxides.25,90,93 Surfaces subjected to fretting wear have a characteristic appearance with red-brown patches on ferrous metals and adjacent areas that are highly polished because of the lapping quality of the hard iron oxide debris. 

After the Lerf model, Dekany et al. proposed a new model based on the diffuse reflectance infrared Fourier transform (DRIFT) measurement of GO [37-39]. The D6kdny model (Fig. 5.1) is composed of ribbons connected by cyclohexane chairs. In the ribbon region, there are functional groups such as tertiary OH, 1,3-ether, ketone, quinone, and phenol (aromatic diol). Recently, there is another GO model proposed by Rourke et al. [40], where GO is oxidative debris adhered graphitic sheets. The graphitic layer is suggested to be only slightly oxidized. 

Rourke JP, Pandey PA, Moore JJ, Bates M, Kinloch lA, Young RJ, WUson NR (2011) The real graphene oxide revealed stripping the oxidative debris from the graphene-Uke sheets. Angew Chem Int Ed 50 3173-3177... 

Fig. 2.4 line remnant imperfection in a friction stir weld shown by (a) macrograph and (b) magnification of oxide debris that... 

Fretting corrosion, which results from slight relative motion (as in vibration) of two substances in contact, one or both being metals, usually leads to a series of pits at the metal interface. Metal-oxide debris usually fills the pits so that only after the corrosion products are removed do the pits become visible. 

Fretting corrosion, as it applies to tin and solder alloys, is the continuous formation and flaking of tin oxide from mated surfaces due to microscopic motion of one contact with respect to the other (see Fig. 9-11) (Antler, 1985). Motion induced by ordinary vibrations is sufficient to produce enough oxide debris to cause contact failure due to... 

Fretting corrosion refers to corrosion damage at the asperities of contact surfaces (Fig. 6.50). This damage is induced under load and in the presence of repeated relative surface motion, as induced, for example, by vibration. Pits or grooves and oxide debris characterize... 

R. Verdejo, S. Lamoriniere, B. Cottam, A. Bismarck, M. Shaffer, Removal of oxidation debris from multi-walled carbon nanotubes, Chem. Commun. (2007) 513-515. 

Fretting corrosion is most prevalent with steel parts where the oxidation process produces an obvious, distinctive, red oxide abrasive dust. Stainless steels are not immune, particularly ferritic t) es. Fretting of aluminum alloys produces a white oxide debris that is also very abrasive. 

The presence of oxide debris indicates that oxide particles were generated by first body degradation (Qi ) and/or by transformation of... 

---