Abrasive effect

Erosion Corrosion. Erosion corrosion is the increase in the rate of metal deterioration from abrasive effects. It can be identified by grooves and rounded holes, which usually are smooth and have a directional pattern. Erosion corrosion is increased by high water velocities and suspended soHds. 

The coating is mechanically removed by the abrasive effects of a high-velocity fluid. 

Metal loss in these areas had produced a smooth surface, free of deposits and corrosion products. The rest of the internal surface was covered by a thin, uniform layer of soft, black corrosion product. The graphitically corroded surfaces of the pump casing provided soft, friable corrosion products that were relatively easily dislodged by the abrasive effects of high-velocity or turbulent water (erosion-corrosion). 

Exposure in a solution that is passivating and yet not far removed from the passive-activity boundary may lead to coiTosion if the exposure involves a strong abrasive condition as well. Pitting of pump shafts under packing handling sea water is an example of this abrasive effect. 

The optimum design of a hydrocyclone for a given function depends upon reconciling a number of conflicting factors and reference should be made to specialist publications. Because it is simple in construction and has no moving parts, maintenance costs are low. The chief problem arises from the abrasive effect of the solids materials of construction, such as polyurethane, show less wear than metals and ceramics. 

Novo Nordisk has also introduced another application of the laccase formulation, namely for stonewashing in combination with cellulase. It enhances the abrasion effect. In this case, a lower dose of the enzyme/mediator slurry is sufficient. Low doses have a mild bleaching effect though the end-result doesn t look like bleaching. Instead the denim looks as if it has been subject to more abrasion. Cellulases can give a stonewashed look to jeans but they have certain limitations when used on their own. If denim finishers want a highly abraded effect, they usually prefer a combination of cellulases and stones to obtain the desired level of abrasion. With the laccase slurry stones are no longer needed. 

Cellulase enzymes break down the surface of the denim, thus releasing the indigo dye. The desired abrasion effect can be obtained totally without the use of purnice stones. 

The abrasive effect of treatments with inorganic salt crystals can reduce tool life. Where machining is necessary, this can be minimized by using tools of abrasive-resistant alloys. 

A. M. Pfarrer, D. J. White, M. Rapozo-Hilo and J. D. Featherstone (2001). Anticaries and hard tissue abrasion effects of a dual-action whitening, sodium hexametaphosphate tartar control dentifrice. J. Clin. Dent., 13, 50-54. 

Addition of metals (15-20% A1 or 50% W) always results in a dilution effect with respect to the observed performance (D, s/ Eq). On the other hand, in the plate dent test a higher performance is realized which is possibly only an abrasion effect of a secondary reaction. 

FIGURE 17.7 Slurry abrasive effect on scratching performance. Ultrahigh-purity (TEOS base) colloidal silica slurry has an excellent oxide scratch behavior. On the contrary, the fumed silica has a tendency to scratch the oxide surface. A step-by-step dilute HF etching reveals smaller and smaller scratches. 

The effect of US power on formed crystals was studied at 0, 10 and 100 W by suspending potash alum crystals in a potash alum saturated solution for 3 h. Conductivity measurements showed that there was neither dissolution nor crystallization, but electron scanning microscopy revealed that the shape of the crystals changed due to erosion. Also, crystal size decreased with increasing US power. Size analysis confirmed the appearance of small particles upon application of US. The amount of smaller crystals formed was modest at a low power (10 W) but increased dramatically with increasing US power an abrasion effect was therefore clearly involved [146]. 

An alternative type of insolnble polystyrene matrix is obtained with lower amonnts of DVB (0.5 to 2%), affording microporons polymers or so-called gel-type resins. These polymers are characterized by the absence of permanent pores and by a low external area. Accordingly, the swelling of the resin in the solvent is of great importance to achieve chemical reactions in appropriate conditions and for this purpose, solvents such as toluene, dichloromethane or THF are generally the more suitable ones. It is also worth noting that this type of structure increases the sensitivity to mechanical abrasive effects and to osmotic pressure." ... 

Fig. 4.5. Anodic potentiostatic curves for steel without friction (1), at siiding fiction against PE (2) and under abrasive effect of ceramics (3) ifp - current of full passivation...

Under microcutting (abrasive effect) metal particles already separate at the beginning of the first cycle, therefore the wear rate in any electrolytes is governed above all by the mechanical factor. 

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