Mortar Coatings

Cement coatings are usually applied as linings for water pipes and water tanks, but occasionally also for external protection of pipelines [7]. Cement is not impervious to water, so electrochemical reactions can take place on the surface of the object to be protected. Because of the similar processes occurring at the interface of cement and object and reinforcing steel and concrete, data on the system iron/ cement mortar are dealt with in this chapter taking into account the action of electrolytes with and without electrochemical polarization. To ensure corrosion protection, certain requirements must be met (see Section 5.3 and Chapter 19). 

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The cathodic effectiveness of the passive steel in cement mortar can be seen in Fig. 5-13. The cell current is measured between a mortar-coated DN 100 pipe section and an uncoated steel ring 16 mm broad as anode. It can be clearly seen that the cell current immediately falls and after 100 days goes toward zero. The same result is obtained by removing the specimens and aerating the mortar coating and repeating the experiment with the same components [51]. 

MAJOR PRODUCT APPLICATIONS high temperature synthesis of wollastonite, synthesis of calcium hydro silicates, sealants, stucco, primers, road marking formulations, resin casting, adhesives, mortars, coatings, paint, lacquers, special papers, construction elements, pin insulators, machine tools, hning for chemical pumps... 

Table 73 Typical Formulations of Estercrete for Mortar Coating.

Although the use of simple diluents and adulterants almost certainly predates recorded history, the use of fillers to modify the properties of a composition can be traced as far back as eady Roman times, when artisans used ground marble in lime plaster, frescoes, and po22olanic mortar. The use of fillers in paper and paper coatings made its appearance in the mid-nineteenth century. Functional fillers, which introduce new properties into a composition rather than modify pre-existing properties, were commercially developed eady in the twentieth century when Goodrich added carbon black to mbber and Baekeland formulated phenol— formaldehyde plastics with wood dour. 

Any of these mortars can be used for unit masonry or for stucco (exterior plaster). The finish coat in conventional interior plastering is composed of either neat time putty or a sanded putty, gauged with Keene s cement or gypsum-gauging plaster. The former is called a whitecoat finish the latter a sandfloat finish. 

P. Schweitzer, Corrosion Resistance Tables Metals, Non-Metals, Coatings, Mortars, Plastics, Elastomers andEinings, andFabrics, 3rd ed., Marcel Dekker, New York, 1992. 

Hydraulic limes (84) may be used for mortar, stucco, or the scratch coat for plaster. They harden slowly under water, whereas high calcium limes, after slaking with water, harden in air to form the carbonate but not under water at ordinary temperatures. However, at elevated temperatures achieved with steam curing, lime—silica sand mixtures do react to produce durable products such as sand—lime bricks. 

After 1860 in the United States, water mains were only occasionally given coatings of tar. About 18% the activities of Engii.sh undertakings were extended to America, where chiefly bare metal pipelines had previously been laid. Water supply pipes were coated internally with bitumen in America after 1912. Vical (1837) in France and J. Bull (1843) in America introduced the widely known cement mortar as a protective material for water pipes 16]. 

Coatings applied for corrosion protection are divided into organic coatings, cement mortar, and enamel and metallic coatings. 

The anodically produced acid is neutralized by the alkaline mortar (CaO). Corrosion is then possible only if the supply of alkali at the steel surface is consumed and the steel becomes active. This process is possible only under certain circumstances after a very long incubation period. Apparently in steel-concrete foundations the possible current densities are so small that this case never arises. The possibility of danger has to be verified with thin outer coatings where deliming has been noticed on the steel surface. 

Lead is relatively easily corroded where acetic acid fumes are present and under such conditions it either should not be used or should be efficiently protected. Generally, any contact between lead and organic material containing or developing acids will cause corrosion for instance, unseasoned wood may be detrimental. Trouble from this cause may be prevented by using well-seasoned timber, by maintaining dry conditions, or by separating the lead from the timber by bitumen felt or paint. Lead is also subject to attack by lime and particularly by Portland cement, mortar and concrete, but can be protected by a heavy coat of bitumen. A lead damp-proof course laid without protection in the mortar joint of a brick wall may become severely corroded, especially where the brickwork is in an exposed condition and is excessively damp. 

In architectural work, particular care must be taken to avoid destructive attack of the anodic film by alkaline mortar or cement during erection, and temporary coatings of spirit-soluble waxes, or acetate-butyrate lacquers are frequently applied to window frames and the like to protect against mortar splashes, which in any event should be removed at the earliest possible moment. 

The primary consideration for all AEM analysis is that the specimen be thin (generally carbon coated electron microscope grid either dry or in a suitable liquid. If a liquid suspension is used in preparing the specimen, it is important that all elements of interest are insoluble in that liquid. Only particles thin enough to meet AEM thin-film criteria (15) should be analyzed quantitatively. Scraping surface particles from a catalyst pellet for specimen preparation may be more useful than grinding the entire pellet. 

Pd on Carbon. The catalyst analyzed here is a commercial hydrogenation catalyst with 5% Pd supported on activated carbon (Alfa). The catalyst was ground in a mortar and pestle and dispersed dry onto a carbon coated Cu grid. While x-ray spectra from heavy metal particles down to 2nm in diameter can be obtained (O by manually directing the electron beam to the particle, digital images of Pd particles at high resolution have not been obtained previously. 

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