Impingement attack tests

Details of jet impingement tests will be found in Section 19.1. Alloys resistant to impingement attack will be considered subsequently. 

Protective films on metals also can be destroyed and corrosion accelerated by the impingement of a high-velocity stream of sea water onto the metallic surface. The inlet ends of condenser tubes, are frequently attacked (Figure 3,a). Jet tests have been devised for ranking the susceptibility of metals to such impingement attack. A corrosion cell is formed between the bare surface directly under the jet (anode) and the adjacent filmed surface (cathode). These jet tests give more dependable information, if natural sea water is continuously supplied to the equipment. 

Electrochemical corrosion measurements were conducted in a modified corrosion testing cell where a combination of a circulating pump and a jet nozzle simulated jet-impingement attack as shown in Figure 4. 

Impingement and erosion-corrosion forms of attack will usually be intensified by the presence of solid particles in the fluid. Variations of the jet test have been proposed to take this effect into account. ... 

Uranium trioxide. The attack of stainless steel pump-loop components by uranium trioxide slurries at 250°C was essentially nil in tests extended for thousands of hours, even on pump impellers with a tip velocity of 120 fps [109]. The lack of attack by circulating uranium trioxide slurries under conditions in which impingement certainly occurred is attributed to the relative softness of the uranium trioxide particles. 

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