Contact corrosion concrete

Little information is available on the performance of copper and of copper alloys in contact with concrete, but concrete sometimes contains ammonia, even traces of which will induce stress-corrosion cracking of copper pipe. The ammonia may be derived from nitrogenous foaming agents used for producing lightweight insulating concrete. 

The corrosion behaviour of iron and steel in contact with concrete is of great importance, not only because of the amount of metal involved, but also because the metal is frequently load-bearing, and the stability and... 

Environments are either gases or liquids, and inhibition of the former is discussed in Section 17.1. In some situations it would appear that corrosion is due to the presence of a solid phase, e.g. when a metal is in contact with concrete, coal slurries, etc. but in fact the corrosive agent is the liquid phase that is always present. Inhibition of liquid systems is largely concerned with water and aqueous solutions, but this is not always so since inhibitors may be added to other liquids to prevent or reduce their corrosive effects — although even in these situations corrosion is often due to the presence of small quantities of an aggressive aqueous phase, e.g. in lubricating oils and hydraulic fluids (see Section 2.11). 

COST 509, Corrosion and Protection of Metals in Contact with Concrete, Final report, R. N. Cox, R. Cigna,... 

P. A. M. Basheer, Surface Treatments for Concrete , COST 509 Workshop Corrosion and Protection of Metal in Contact mth Concrete, Sevilla, 4-9 September 1995. 

COST 509, Corrosion and Protection of Metals in Contact with Concrete,... 

COST 509 Corrosion and protection of metals in contact wifli concrete. Draft final report. Workshop September 1-3, Heriot-Watt University, Edinburgh, 1996,127. 

One corrosive agent to which refractory concrete may be exposed during service is carbon monoxide (CO). To ensure an acceptable resistance of hydrated calcium aluminate cement to this agent, the cement must not contain iron oxide, which may undergo chemical reduction to bivalent iron imder these conditions. In situations in which hydrogen may come into contact with concrete based on calcium aluminate cement, the silica content of the binder may be critical, and thus should be kept low. 

In reinforced concrete basins of waste water treatment plants, there are extensive steel mats which act as cathodes with a large surface area. If these steel mats, which are in the waste water, are in electrical contact with components of unalloyed steel, it is possible that an electrochemical cell is formed by contact corrosion [llj. 

Several forms of corrosion are associated with anchors in concrete, including contact corrosion, crevice corrosion, pitting, and inter-crystalline stress corrosion. As with... 

Fig. 4. Corrosion at phase contacts of concrete. [From Hedvall(2).]...

Prolonged contact with concrete, even in the presence of humidity, leads only to a superficial attack, shown by testing results with concrete blocks with embedded unprotected aluminium (Table G.4.1) that were exposed to various media, including marine atmosphere [3]. The zone of emergence in the air is not prone to corrosion (see Section B.2.7). 

Corrosion is generally taken to be the waste of a metal by the action of corrosive agents. However, a wider definition is the degradation of a material through contact with its environment. Thus, corrosion can include non-metallic materials such as concrete and plastics and mechanisms such as cracking in addition to wastage (i.e. loss of material). This chapter is primarily concerned with metallic corrosion, through a variety of mechanisms. 

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. 

When mature concrete is contaminated by chloride, e.g. by contact with deicing salts, the cement chemistry is more complex, and less chloride is taken up by the cement hydrate minerals and a larger proportion is free in the pore solutions and can therefore pose a greater hazard. When embedded steel corrodes, the production of a more voluminous corrosion product pushes the concrete from the steel with resultant cracking and spalling of the concrete. 

The porosity of the concrete at an advanced state of maturity is increased in the presence of calcium chloride and, therefore, will allow a greater opportunity for air and moisture to come into contact with the steel reinforcement, encouraging corrosive effects. In practice, with reinforcement cover meeting the relevant codes of practice, this effect is regarded as of minimal significance. 

A. Carnot, I. Frateur, S. Zanna, B. Tribollet, I. Dubois-Brugger, and P. Marcus, "Corrosion Mechanisms of Steel Concrete Moulds in Contact with a Demoulding Agent Studied by EIS and XPS," Corrosion Science, 45 (2003) 2513-2524. 

Several methods have been proposed to nonintrusively measure the thicknesses of walls, corrosion profiles, and macrodefects [i.e., 49], Two methods at room temperature that require point contact with the cold face of the furnace are known. The first is impact-echo method, used in construction concretes and pavements (Sect. 1.4). The second method is the frequency-modulated continuous-wave (FM-CW) radar technique [50], which can produce wall thickness data in real time. 

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