Alkaline corrosion

The Al-HjO diagram does show, however, the danger that may arise due to an increase in pH when the metal is cathodically protected in near-neutral solutions indeed, the possibility of alkaline corrosion has seriously limited the use of cathodic protection for aluminium structures. 

There are several incidents in the text where glass has been involved as a direct cause, either because of its chemical properties (alkalinity, corrosive attack), or its physical properties (actinic transparency, or mechanical limitations under stress). Some of these incidents may be found under the entries ... 

Civilization depends on the protection of metals, for most of them are unstable in normal environments unless they are protected by some kind of oxide film. The basic idea about the theory of corrosion is that the metal gets involved in a kind of local fuel cell in which it consumes itself. The partner to most of this self-dissolution is the deposition of hydrogen (favored in acid solutions) or the reduction of oxygen (favored in alkaline). Corrosion is measured in many ways, but the quick way in the laboratory is to move the potential a little bit away ( 5 mV) from the corrosion potential in both anodic and cathodic directions and measure the corresponding current. A simple equation takes the data from this type of measurement and produces the corrosion rate. 

Gorman RL, Khin-Maung-Gyi MT, and Klein-Schwartz W (1992) Initial symptoms as predictors of esophageal injury in alkaline corrosive ingestions. American Journal of Emergency Medicine 10 89-194. 

The most frequent injury following alkali ingestion is esophageal burns. Diffuse circumferential esophageal burns are more common in patients ingesting liquid forms of concentrated alkaline corrosives granular forms tend to produce more oral burns and... 

Esophageal cancer has been related to the use of alcohol and nitrosamines and possibly chewing betel nut (popular in parts of Asia). Other risk factors include a history of ingestion of alkaline corrosive agents, including lye. Nutritional deficiencies have also been linked to this type of malignancy. 

Ellipsometry can be used to gain information about the films formed in the three uniform corrosion regimes. Details are given here about two of those cases firstly the barrier or valve metal oxide layers, which optically are nearly ideal films, and secondly alkaline corrosion, which gives some insight into the applications of ellipsometry to non-uniform films and roughened metallic surfaces. 

Barium hydroxide Ba(OH)2 Highly alkaline, corrosive to Reaction with phosphorus... 

I. Mechanism of toxicity. Ammonia gas is highly water-soluble and rapidly produces an alkaline corrosive effect on contact with moist tissues such as the eyes and upper respiratory tract. Exposure to aqueous solutions causes corrosive alkaline injury to the eyes, skin, or gastrointestinal tract (see Caustic and Corrosive Agents, p 157). 

C. Skin or eye contact with gas or solution. Serious alkaline corrosive bums may occur. 

B. Specific drugs and antidotes. There is no specific antidote for these or other common caustic bums. The use of corticosteroids in alkaline corrosive ingestions has been proved ineffective and may be harmful in patients with perforation or serious infection. 

B. Low-phosphate detergents and electric dishwasher soaps often contain alkaline corrosive agents such as sodium metasilicate, sodium carbonate, and sodium tripolyphosphate. 

C. Alkaline corrosive burns result from misuse of the home manufacture kits a dangerously basic solution is produced when excess base is added, the reaction is incomplete, or there is inadequate back titration with acid. (The solution can also be acidic from excessive back titration.)... 

Batteries that require a liquid electrolyte are called wet batteries. Corrosive battery fluid refers to either acid electrolytes syn. battery acid, like the common lead-acid automobile battery which uses a solution of sulphuric acid, or alkali electrolytes syn. alkaline corrosive battery fluid, like potassium hydroxide (1310-58-3) solutions in nickel-cadmium and other alkaline battery systems. Dry batteries or dry cells, like all primary batteries, use electrolytes immobilized in pastes, gels, or absorbed into separator materials. Some batteries are loaded with a dry, solid chemical (e.g., potassium hydroxide) which is diluted with water to become a liquid electrolyte. The hazards associated with handling and transportation prior to use are thereby reduced. 

Cathodic protection can also be applied to prevent pitting. Regarding aluminium, strong cathodic polarization should be avoided because this can lead to a large increase of pH close to the metal surface, which can cause so-called alkaline corrosion (compare with the Pourbaix diagram for aluminium in Figure 3.11, Section 3.8). Use of sacrificial anodes of Zn or A1 alloys is therefore safer than impressed current. 

Of the bum injury patients admitted to a specialized Regional Bum Center in Toronto, Ontario, Canada, over an 8-year period, the 24 chemically injured patients made up 2.6 % of the total [29], Occupationally related chemical exposures accounted for 75 % of these injuries, and the involved chanicals included hydrofluoric acid, sulfuric add, black liquor (a heated mixture of sodium carbonate, sodium hydroxide, sodium sulfide, sodium thiosulfate, and sodium sulfate), lyes (alkaline corrosives), phenol, and potassium permanganate. Complications were seen in 58 % of chemically injured patients, including chemical ocular injuries, wound infections, tendon exposures, toe amputation, and systemic toxicity. Of these 24 patients, 14 required extensive surgical debridement and skin grafting. One patient with a 98 % TBSA chemical skin injury died. Of those patients who had typical decontamination measures such as removal of contaminated clothing... 

The E-glass fibres in gypsum matrices are not subjected to alkaline corrosion and are applied in partition walls, internal cladding, etc., (cf. Sections 3.2 and 14.5). 

Textile reinforcement with natural vegetal fibres or with glass fibres is particularly vulnerable to alkaline corrosion (cf. Sections 5.3 and 5.8). 

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