Corrosion limits

Some workover fluids can produce high corrosion rates. Corrosion control can be accomplished through H control, inhibitors or bactericides. The practical corrosivity limit is 0.05 lb/ft= per operation. 

Select the engine coolant or antirust with care to ensure adequate corrosion protection. Use only those products conforming to recognized standards such as ASTM D 3306 for engine coolant. Additionally, if your vehicle engine contains major cast aluminum components, be certain the engine coolant meets the heat rejection corrosion limits in ASTM specification D 3306 as determined by ASTM Test Method for Corrosion of Cast Aluminum Alloys in Engine Coolants Under Heat-Transfer Conditions (D 4340). 

The second method uses semi-conducting electrodes in a photochemical cell to convert light energy into chemical energy. The semiconductor surface serves two functions, to absorb solar energy and to act as an electrode. However, light-induced corrosion limits the useful life of the semiconductor. 

The LiF-LiCl-LiBr electrolyte has the highest conductivity, but due to the high liquidus the battery can work only at a temperature of 475°C, where corrosion limits the cycle life. 

Low-alloys steels are used for wellbore tubulars. Corrosion limits for jointed tubing is arbitrarily set at <0.05 pounds per square foot of tubing surface area which represents a loss of 1/1000 of an inch in wall thickness. Pitting deeper than 0.015 inch (0.381 mm) is not acceptable. 

As was expected, the chloride content decreased with the increase in depth. The accepted corrosion limit for chloride content in concrete is 1.5 lb/cy. The highest values corresponded to the specimens containing 4 percent of HDPEflake (6.27 lb/cy), and 4 percent of PET (6.25 lb/cy). The concretes containing these same fillers in a 1-percent proportion also reached high chloride levels, e.g. 5.16 and 5.11 lb/cy of concrete. The control specimens reached a chloride level of 5.67 lb/cy which is approximately the average between the two values of HDPE and PET specimens. The rest of the plastic-concrete combinations exhibited a lower chloride level than the control specimens but always above the corrosion limit of 1.5 lb/cy of concrete. 

In water, corrosion limits the use of aluminum to temperatures near 100°C, unless special precautions are taken. In air, corrosion limits its use to temperatures slightly over 300°C. Failure is caused by pitting of the otherwise protective Al(OH)3 film. The presence of chloride salts and of some other metals that form strong galvanic couples (for example, copper) can promote pitting. 

In the early 1980s, the corrosion of structural steel supports due to chloride ions liberated from PVDC-modified mortar which had been used to repair an old brick building, led to a civil suit in the United States l l therefore, PVDC latex is not currently used as a cement modifier in the United States and other countries. In a laboratory study, the liberation of chloride ions is observed in such a chloride-containing polymer, and a possibility of the conosion of the reinforcing bars which is induced by the chloride ions in reinforced concrete structures is suggested.l H The use of PVDC-modified mortars with polymer-cement ratios of 5% or more causes the liberation of sufficient chloride ions to exceed flie tolerable corrosion limits for the reinforcing bars in reinforced concrete structure. 

Degussa [40] Avoid corrosion limiting contact time 0.25% wt Pd-Au (95 5) on a-Al203... 

In general, the corrosion resistance of ferritic stainless steels is 5-10 times greater than that of austenitic steels in Pb-Li[2], For a corrosion limit of 20 um/yr, the peak operating temperature is 500°C for ferritic steels and 410°C for austenitic steels[3]. Consequently, the use of austenitic stainless steels is not recommended [6]. For temperatures in excess of 450°C, ferritic steels require Zr or Ti corrosion inhibitor additives, so their suitability for temperatures as high as 750°C is questionable. 

Large air ingress No systems installed — - Graphite corrosion limited by naturally limited air flow through core... 

Hydrogen peroxide y 1 2 75 corrosive limited usefulness 75 unlimited... 

Figure 4.37 Evans diagram for corrosion limited by oxygen transport.

Corrosion limited by the transport of reaction products Maximum rate of dissolution... 

Operation beyond designed temperature range Operation beyond design limits Bad material selection/fatigue test not carried Sustained operation beyond corrosion limit Change of services Extremely corrosive atmosphere... 

For specific examples of how to apply these corrosion limits for low pressure and high pressure steel cylinders, refer to CGA C-6 [10]. 

Interior corrosion is best evaluated by a hydrostatic test combined with careful visual inspection. Ultrasonic thickness-measuring and flaw-detection devices may be used to evaluate specific conditions. Corrosion limits for both low and high pressure steel cylinders were dis-... 

Localized pitting or line corrosion will not be detected by the hydrostatic test. These types of corrosion may cause significant localized stresses, and care must be exercised in judging whether or not the conditions are extensive enough to require rejection. Use the criteria on corrosion limits discussed under the external visual inspection section. 

It is beyond the scope of this presentation to fix corrosion limits for all types, designs, and sizes of cylinders and include them here. General criteria for low pressure and high pressure steel cylinders is given in the following paragraphs. 

---