Corrosion operating equipment

It is occasionally desirable to expose corrosion-test specimens in operating equipment without the use of specimen holders of the type... 

Fluoroboric acid is produced commercially by the reaction of 70% hydrofluoric acid with boric acid. Fluoroborate solutions must be treated like hydrofluoric acid and handled in corrosion resistant equipment consisting of polyethylene, polypropylene, or neoprene-type rubber. The major use of fluoroboric acid is as an intermediate in the preparation of fluoroborate salts. It is also used in electroplating aluminum and in metal cleaning operations. 

High temperature and high pressure processing of materials often involves the use of supercritical fluids. Corrosion studies are quite essential for evaluation of the equipment in supercritical fluid operations. Previous electrochemical measurements for alloys in supercritical fluids are rare (1-1). The reported measurements (3) show that passivation of iron alloys is different at supercritical conditions compared to ambient conditions. The study of the electrochemistry of iron alloys can lead to control of corrosion of equipment utilizing the alloys. Thermodynamic analysis provides the information about stable species, i.e. corrosion products under given temperatures and pressures. 

Some of these strippers suffered from one or more drawbacks such as potential toxicity to workers exposed to them, environmental and pollution problems in disposal after use, volatility, corrosion of equipment, and the safety hazard of operating at temperatures above the flash point of the stripper. They were also plagued by difficulties and the high cost associated with disposing of them in an environmentally acceptable manner after use. The semiconductor industry has to a large extent migrated away from them for the aforementioned reasons, and some of the chlorinated resist strippers such as chloroform are now banned from the semiconductor industry. 

Sea Water. To conserve fresh water, coastal chemical plants use sea water for cooling. That means higher fixed costs for corrosion-resistant equipment, but operating economies often compensate for this. Recirculated fresh water can be bottled up in a closed system and cooled with sea water. Conversion of sea water, either by ion exchange or distillation, is too costly for industrial use, approximating 0.80 to 1.30 per 1,000 gal. 

Battery acid Battery fluid, acid, 8 Battery fluid, alkali, 8 Battery-powered equipment, 9 Battery-powered vehicle, 9 Battery, wet, filled with acid or alkali with automobile (or named self-propelled vehicle or mechanical equipment containing internal combustion engine) Battery, wet, with wheelchair Cells containing sodium, 4.3 Corrosive battery fluid Electric storage batteries Electrolyte (acid) for batteries Electrolyte (acid or alkali) for batteries Electrolyte (alkali) for batteries Heat producing article, battery operated equipment, 9 Lithium batteries, 9 Lithium batteries contained in equipment, 9 Lithium batteries packed with equipment, 9 M86 fuel, 3.2... 

Premature failure of bridges or structures because of corrosion can also result in human injury or even loss of life. Failures of operating equipment resulting from corrosion can have the same disastrous results. 

Chapter 4 dealt with the different test methods available for assessing corrosion related properties of reinforced concrete. Most of the techniques are applied with hand-held battery operated equipment and a one off reading is taken. In some cases such as cover meter measurements that reading will not change. In others, such as concrete resistivity, corrosion rate or corrosion potential (reference electrode potential) it will change as aggressive agents in the environment move into the concrete and lead to or accelerate corrosion. 

Operational problems involving miscible processes include transportation of the miscible flooding agent, corrosion of equipment and tubing, and separation and recycling of the miscible flooding agent. 

A European chemical factory had corrosion/erosion problems in an inlet pipe, particularly weld corrosion. Traditional UT was seen to be unreliable because the uneven surfaces and varying wall thickness (not to mention the cramped space) made it a very challenging task for even the most experienced UT operator. Equipping the inlet with a sensing matrix allows the factory to regularly inspect for the onset of corrosion, with more intensive inspection if corrosion occurs. UT is also difficult to apply in high temperature. 

Virtually all definitive test work is done in a pilot plant or plant. The final test is performance of actual operating equipment. A systematic, quantitative inspection program is the final measure of success of a corrosion control program. All other methods are evaluated in terms of how closely they approximate this method. Other methods used are listed and described briefly below. 

The purpose of corrosion monitoring is to assess or predict corrosion behavior of the system. Basically, there are two objectives to monitoring (1) to obtain information on the condition of the operational equipment, and (2) to relate this information to the operating variables (i.e., pH, temperature, water quality, chemical treatment, etc.). Meeting these objectives will provide the following results ... 

Low resistivities and high chloride concentrations in the soil may lead to corrosion of buried steel pipehnes or structures. Cathodic protection should be considered for all buried steel pipehnes or structures. Where cathodic protection is not provided, corrosion monitoring equipment should be incorporated into the design to allow the operating staff to monitor the condition of the pipelines or structures. Nonwelded joints should be bonded for electrical continuity. In addition, coatings should also be considered. Coatings may be used alone or in con-jimction with cathodic protection. 

Corrosion of filters occurs in the transpassive state. Their cathodic protection is based on the polarization of steel to a potential characteristic of the passive state. Garner (1998) states that over 120 CP installations have been applied, mainly in North America, for the protection against corrosion of equipment made of austenitic stainless steels operating in bleacheries. More information is given by Webster (1989) and Singbeil and Garner (1987). 

Modern processes emphasize low costs (raw materials, operation, maintenance, etc.), improved efficiency, high quality, safety, and environmental friendliness. These emphases often require that chemical reactions take place at elevated temperatures and pressures in the presence of a catalyst. Therefore, as the CPI modernizes its technologies, process environment may become more corrosive and require more corrosion-resistant equipment to cope with corrosion problems. 

If the separated products are required relatively pure, the disadvantages of the indirect operations incurred by addition of a foreign substance are several. The removed substance is obtained as a solution, which in this case must in turn be separated, either to obtain the pure substance or the added substance for reuse, and this represents an expense. The separation of added substance and product can rarely be complete, which may lead to difficulty in meeting product specifications. In any case, addition of a foreign substance may add to the problems of building corrosion-resistant equipment, and the cost of inevitable losses must be borne. Obviously the indirect methods are used only because they are. in the net, less costly than the direct methods if there is a choice. Frequently there is no choice. 

Oxygen, even in very small amounts, may cause serious corrosion in feedwater lines, stage heaters, economizers, boiler metal, steam operated equipment and condensable piping. It must, therefore, be removed from the closed system. The solubility of oxygen varies with both pressure... 

---