Corrosion dynamics

Lister, T.E., and P.J. Pinhero. 2002. Scanning electrochemical microscopy study of corrosion dynamics on type 304 stainless steel. Electrochem Solid-State Lett 5 (11) B33. 

After 32 days at 88°C in 33% Prestone II (a commercial engine coolant solution that contains silicate inhibitors), ZA-8 and Alloy 3, either as-cast or polished, showed no corrosion. Dynamic tests confirmed the suitability of ZA-8 at 118°C. ZA-27 displayed intergranular attack when tested as-cast but not when its surface was polished before testing. Possibly, the soft, zinc-rich phase had been smeared over the whole surface during polishing. 

A.212. This section should describe the design bases for qualification of components to resist such environmental factors as vibration, thermal expansion, radiation, corrosion, dynamic effects, mechanical loadings and high pressure, high temperature, humidity, water, steam, chemicals, low temperature or vacuum. Qualification tests and analyses that have (or will be) performed should be described. 

In general, the influence of grain size on the oxidation resistance of CG metals can be divided into negative and positive effects." " A negative example is IGC, in which the corrosion behavior of metals is controlled by the corrosion dynamic... 

Another type of membrane is the dynamic membrane, formed by dynamically coating a selective membrane layer on a finely porous support. Advantages for these membranes are high water flux, generation and regeneration in situ abiUty to withstand elevated temperatures and corrosive feeds, and relatively low capital and operating costs. Several membrane materials are available, but most of the work has been done with composites of hydrous zirconium oxide and poly(acryhc acid) on porous stainless steel or ceramic tubes. 

Use and Uimitations of Electrochemical Techniques A major caution must be noted as to the general, indiscriminate use of all electrochemical tests, especially the use of AC and EIS test techniques, for the study of corrosion systems. AC and EIS techniques are apphcable for the evaluation of very thin films or deposits that are uniform, constant, and stable—for example, thin-film protective coatings. Sometimes, researchers do not recognize the dynamic nature of some passive films, corrosion produc ts, or deposits from other sources nor do they even consider the possibility of a change in the surface conditions during the course of their experiment. As an example, it is note-... 

Fig. 2-18 J U) curves and critical potential range for intergranular stress corrosion (hatched) for a hardened 10 CrMo 9 10 steel (ASTM P21) in boiling 35% NaOH — potentio-dynamically measured with +0.6 V h - - potential change after every 0.5 h At/ = +0.1 V x-x-x potential change after every 0.5 hAf/ = -0.1 V.

In contrast to pipelines and harbor installations, platforms are dynamically loaded. Therefore in the choice of steels, in addition to strength and types of machinability, the risk of corrosion fatigue and strain-induced stress corrosion must be taken into account in combination with cathodic protection (see Sections 2.3.3 to 2.3.5). 

Abrasion. When evaluating the possibility of installing a seal in a liquid that has entrained solids, several factors must be considered. Is the seal constructed in such a way that the dynamic motion of the seal will be restricted by fouling of the seal parts The seal arrangement that is usually preferred when abrasives are present is a flushed single inside type with a face combination of very hard material. Flowever, factors such as toxicity or corrosiveness of the material may dictate that other arrangements be used. 

Stress Corrosion Up to maximum of Branched cracks, Stainless steels in Almost any grade of Stresses—dynamic Use material which... 

Embrittlement embrittlement and for improperly heat treated steel, both of which give intergranular cracks. (Intercrystalline penetration by molten metals is also considered SCC). Other steels in caustic nitrates and some chloride solutions. Brass in aqueous ammonia and sulfur dioxide. physical environments. bases of small corrosion pits, and cracks form with vicious circle of additional corrosion and further crack propagation until failure occurs. Stresses may be dynamic, static, or residual. stress relieve susceptible materials. Consider the new superaustenitic stainless steels. 

The determination of the first bending critical speed is well established however, there is also concern with regard to the rotor support system s sensitivity to exciting forces. These come from unbalance and/or gas dynamic forces arising during operation in service. Operation with dirty corrosive gas will soon cause rotor unbalance. The rotor dynamics verification test is concerned with synchronous excitaticm, namely unbalance. The test must also verify that the separation margins are to specification. 

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