Types corrosion

Extensive field experience has shown the 50 Cr/50 Ni and 60 Cr/40 Ni alloys to offer the best answer to controlling fuel oil ash corrosion. Type 446 stainless steel also shows acceptable corrosion rates but must be used judiciously due to its low strength at elevated temperatures and weldability. Since components of 50 Cr/50 Ni in contact with vanadium-sodium fuel ash melts still suffer high corrosion rates, they should be designed to minimize the amount of surface area available where ash may accumulate. 

Filiform Corrosion-type of corrosion that takes place under a film in the form of randomly distributed hairlines. 

Corrosion type Environment Favourable Neutral Unfavourable... 

The importance of MIC has been underestimated, because most MIC occurs as a localized, pitting-type attack. In general this corrosion type results in relatively low rates of weight loss, changes in electrical resistance, and changes in total area affected. This makes MIC difficult to detect and to quantify using traditional methods of corrosion monitoring [1447]. 

The first step is the evaluation of thermodynamic and kinetic data by quantitative energy calculations and qualitative considerations as discussed in Chapter 2. The results may provide a satisfactory answer as to whether the reaction can be performed in the open laboratory or requires a high-pressure cell arrangement on the small scale. Further evaluations are required for scale-up. Toxicity, corrosivity, type of apparatus, size, and other criteria must also be considered. 

The overall question on improving treatment is not yet answered. Up to now, there is little knowledge on corrosive type, extent and time of exposure of tissues ans cells which could be acceptable. In the same order, there is up to now no description on how and when a treatment is predictable as successful and when it will not prevent damage. 

It is certainly my experience that the most common and catastrophic accidents in process units are related to corrosion-type failures. I cannot actually bring to mind any equipment vessels which were overpressured and failed because a relief valve did not open. 

Pitting corrosion (Table 4.8) involves pit initiation (breakdown of passive film) followed by pit growth. The chloride ion induces pitting corrosion. Type 304 steel undergoes pitting more readily than Type 316 steel. The molybdenum in 316 steel is responsible for its reduced susceptibility to pitting corrosion. Type 316L steels contains... 

Figure 6.34 Some corrosion types of mechanically assisted degradation3...

The new dress-cap substrate material should be either fiber-reinforced plastic (FRP) or Type 316 stainless steel. Being a nonmetallic insulator, FRP would eliminate any possibility of galvanic corrosion. Type 316 stainless steel demonstrates good passivity in urban atmospheres and has been successfully used in contact with copper.1... 

On the chemistry side, the key knobs are pH, concentration of oxidizer, and abrasive content, given a relatively developed slurry formulation. Among these factors, pH has the most profound impact on removal rate as it determines how deep the oxidization process can penetrate into the tungsten film. A deeper penetration of the tungsten film allows higher removal rate provided that there is sufficient mechanical force to remove the softened film. The mechanical forces include downpressure, abrasive particles, and pad. In other words, at any given pH and oxidizer concentration, there is a removal rate limit. Within the limit, the removal rate follows the Preston equation. If the mechanical force is above this limit, scratch-type defects will be present. If the mechanical force is severely below what is needed to remove all the softened fill, corrosion-type defects will dominate the surface. 

Less reactor fouling for corrosive type of catalyst because the catalyst used is normally held within some structures and hence will not be in direct contact with the reactor wall. 

Urticants produce instant, almost intolerable pain. They cause local tissue destruction immediately on contact with skin and mucous membranes. Sensations range from mild prickling to almost intolerable pain resembling a severe bee sting. Direct contact of the agent with the skin produces a corrosive type lesion. Skin lesions may not fully heal for over 2 months. Inhalation of Urticant vapor can cause lung membranes to swell and become filled with liquid (pulmonary edema). Death may result from lack of oxygen. 

Single-component corrosion types, important for heat exchanger design and operation, are as follows (1) uniform attack corrosion, (2) galvanic corrosion, (3) pitting corrosion, (4) stress corrosion cracking, (5) erosion corrosion, (6) deposit corrosion, and (7) selective leaching [153],... 

Standard austenitic stainless steels such as type 316 (18 Cr 10 Ni 3 Mo) have useful if limited resistance, to acids and reasonable resistance to pitting corrosion. Type 304 (18 Cr. 10 Ni) stainless steel has a good resistance to nitric acid. Austenitic stainless steels have relatively low strength, poor antierosion and abrasion properties and do not possess the ability to resist stress corrosion cracking. 

The most widespread corrosion types are point corrosion or pitting, filiform, crevice, contact and intercrystalline corrosion. The highest danger for the metal-polymer system is presented by the crevice type of corrosion. 

FYom the multitude of intricate corrosion processes in the presence of mechanical action (friction, erosion, vibration, cavitation, fretting and so on) it is justified to touch upon corrosion types joined under a single failure mode induced by mechanical stresses. These are the stresses that govern the corrosion wear rate of metals during friction. Such processes are usually called corrosion stress-induced cracking in the case that the mechanical action is effective only in one definite direction, or otherwise termed corrosion fatigue in the case that compressive and tensile stresses alternate within cycles. In spite of the differences between the appearance of these corrosion types, they have much in common, e.g. fundamental mechanisms, the causes, and they overlap to a certain degree [19]. 

For each aTToy, experiments Have been done in which specimens were exposed unstressed, to solutions that can cause cracking, under a variety of conditions. If broken in air immediately after removal from the solution, specimens exhibited a low value of Zf and fracture surfaces characteristic of stress corrosion cracking. If lapse of time occurs between removal from solution and stressing, specimens exhibited increased values of Sf and decreased amounts of stress corrosion-type fracture with increasing length of lapse of time. This behavior is characteristic of hydrogen embrittlement fracture and has been interpreted as such for the four types of alloys described. These are simple but very clear experiments. 

Fig. 4 Example of the results of crevice corrosion. Type 304 SS exposed to 6 wt.% ferric chloride for 48 h at room temperature with castellated crevice washer applied around center hole. Pitting also occurred at several sites outside the crevice. The draining of the occluded solution from the crevice sites (and pits) led to the river pattern of...

Figure 1.14 Corrosion types of mechanically assisted degradation. (Reproduced with permission of NACE International from Reference 3.)...

Material Corrosion Type Tap Water Quality Deterioration... 

There are some common areas of significant corrosion impact for major home appliances and comfort conditioning appliances. The corrosion types are internal corrosion from process water and external corrosion from wet conditions. 

Corrosion Types with Different Cathodic Reactions... 

Corrosion Types with Different Cathodic Reactions 6 = C f(L) Re"" Sc"" oc v"", where... 

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