Inhibition, corrosion capacity

The rare earth composition of commercial electrodes is also related to electrode corrosion. This was noted by Sakai et. al. [44], who found that the presence of Nd or Ce inhibited corrosion when substituted in part for La in La, fZt(NiCoAl)5 (Z = Ce or Nd) electrodes. However no explanation for the effect was noted. Willems [22] prepared an electrode of La0XNd02Ni25Co24 Si0l which retained 88% of its storage capacity after 400 cycles. He attributed its long cycle life to a low VH of 2.6 A3. 

Cobalt is invariably present in commercial MHt battery electrodes. It tends to increase hydride thermodynamic stability and inhibit corrosion. However, it is also expensive and substantially increases battery costs thus, the substitution of Co by a lower/cost metal is desirable. Willems and Buschow [40] attributed reduced corrosion in LaNi 5 vCoi (x= 1 -5) to low Vn. Sakai et al. [47 J noted that LaNi25Co25 was the most durable of a number of substituted LaNi5 iCoi alloys but it also had the lowest storage capacity. 

Both factors are sensitive to alloy composition, which can be adjusted to produce electrodes having an acceptable cycle life. In AB5 alloys the effects of Ce, Co, Mn, and A1 upon cycle life in commercial AB5 -type electrodes are correlated with lattice expansion and charge capacity. Ce was shown to inhibit corrosion even though lattice expansion increases. Co and A1 also inhibit corrosion. XAS results indicate that Ce and Co inhibit corrosion though surface passivation. 

Admixture formulations containing two or more compounds (multicomponent) in which each component plays a specific role or compliments the corrosion resistance capacities of the other are also used. For example, a mixture of calcium nitrite and calcium formate is used to both accelerate strength of the concrete and inhibit corrosion of the steel during steam curing. 

Active corrosion inhibition system Capacity of injection 3.28 1.96... 

Although the presence of different compounds of the lanthanide elements seems to have an undoubted beneficial effect in the resistance to wear in different enviromnents, and reducing the loss of material, the mechanism by which these improvements occur is still very controversial. Although there is no doubt of the capacity of the lanthanide elements to inhibit corrosion, and their corresponding synergic effects with mechanical factors. However, any influence of these elements on purely mechanical factors, and any modification of mechanical contact are still not clear. 

It has been shown that water supersaturated with calcium carbonate often develops tubercular deposits which do not inhibit corrosion on mild steel. This behavior is typically associated with water of low buffer capacity. Puckorius also warned against using saturation-level-derived indices as the basis for predicting corrosion problems in cooling systems. 

In 1975 Mallory introduced their new glass-to-metal hermetic seal to reduce sulphur dioxide losses from the cell and consequently reduce capacity loss on storage and inhibit corrosion effects. Such cells have been stored for 1.75 years at 21°C and 4 months at 72°C... 

Similarly, cooling water that is fully softened tends to lack sufficient buffering capacity and creates the potential for significant corrosion within the cooling system, so care and attention to design detail are needed if future corrosion problems are to be avoided. Also, most chemical treatments incorporate polymers or phosphonates of some sort to provide a measure of corrosion inhibition. These products usually require the presence of at least 25 to 35 ppm of calcium hardness to provide satisfactory inhibition. 

The presence of water, as mentioned earlier, can have several detrimental results among which is the formation of gas hydrates—snowlike, crystalline compounds composed of small amounts of methane, ethane, propane, or isobutane and water. The formation of these hydrates is aided by the presence of liquid water and areas of turbulence. The formation of these hydrates increases the pressure drop along the pipeline, thereby decreasing its capacity the presence of liquid water also can contribute to some corrosion. The formation and inhibition of these hydrates will be discussed in Section XII. In this section about gas treatment, the removal of hydrogen sulfide and other sulfide forms from the natural gas is discussed along with removal of carbon dioxide. A number of processes have been commercialized in this area and a few of them will be described here. 

Crystamet . [Crosfield Rhone-Poulenc Basic] Sodium metasilicate penta-hydrate for formulating specialty detergents and contributing buffering capacity and corrosion inhibition of soft metals and ceramic glazes. 

Most known procedures of this group of methods are called oxidation and sulfuration tests. In the former case a metal test specimen wrapped in a VCI film material is placed in a desiccator (about 10 1 in capacity). The internal atmosphere reaches 100% RH using 20 cm of water. The desiccator is blocked up and is placed in a 50° C constant-temperature tank or in normal-temperature room to promote the growth of rust. In sulfuration test the desiccators about 2.5 1 capacity are used. After having adjusted the inside atmosphere to reach 93% RH using 10 cm of a saturated solution of Na2S04, a test metallic strip wrapped in inhibited film material is placed inside. The tests are continued until a corrosive phenomenon is observed. 

Anodic inhibition of stress corrosion cracking was first provided on an industrial scale in a large plant for the production of hydrogen by electrolysis of potassium hydroxide solution. After preliminary trials on a laboratory scale, the chemical industry s first anodically protected large-scale plant, a sodium hydroxide solution evaporator with a capacity of 142 t, was put into operation in 1968. Since then, plants have been equipped in the same way (Grafen 1971). 

Transport of gasoline and other refined products in steel pipelines may result in corrosion products that can create a product contamination problem. Internal corrosion of the pipeline can also have an adverse effect on pipeline capacity. Corrosion results from condensation of a water film on the pipe wall plus dissolved air or SRB in the product. Corrosion control is commonly achieved by adding a corrosion inhibitor. Evaluation of inhibitor performance can be done using NACE Test Method for Antirust Properties of Cargoes in Petroleum Product Pipeline (TM0172). This test method is a modification of ASTM D 665, Test Method for Rust-Preventing Characteristics of Inhibited Mineral Oil in the Presence of Water. 

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