Corrosion protection reinforcement

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). 

The decision to cathodically protect reinforced concrete structures depends on technical and economic considerations. Cathodic protection is not an economic process for small area displacements of the concrete due to corrosion of the reinforcing steel arising from insufficient concrete covering. On the other hand, the... 

Rectifier housing with glass fiber-reinforced base, housing connection box, meter table, corrosion protection rectifier 10 A/20 V, terminal strips, cable terminal and wiring, completely installed DM 8500... 

Considerable alterations have been made in the chapters concerned with technical applications which are the result of advances in electrochemical corrosion protection in general practice. Here also, abbreviation and omission of less relevant parts of the older editions have had to be made to create space for more recent information. Recent applications in the chemical industry have necessitated a complete rewriting of the industrial chapter. A new chapter is included on the cathodic protection of steel reinforcement in concrete. 

Normally concrete is reinforced with plain carbon steel, but under conditions where rapid carbonation can occur or there is a risk of chloride contamination, corrosion-protected or more corrosion-resistant reinforcing steels may be necessary. Currently there are three reinforcing bars which have enhanced corrosion resistance ... 

The corrosion of reinforcing steel due to chloride contamination in concrete is an increasingly serious problem, and interest in cathodic protection as a means of mitigating corrosion on reinforced steel has become of some importance in recent years. 

The data presented in this section illustrate that, with the exception of those accelerating water-reducing admixtures containing calcium chloride, there is an abundance of evidence to support the conclusion that water-reducing admixtures of lignosulfonate chemical form certainly will not accelerate any kind of corrosion with reinforcement and, when used to reduce the water-cement ratio, will form a more permeable and durable protective cover for the reinforcement. In view of the chemical nature of the other types of materials such as the hydroxycarboxylic acids and hydroxylated polymers, it seems most likely that these materials too would have no deleterious effect in this respect. 

Virmani, Y.P., Clear, K.C. and Pasko, T.J. (1983). Time to Corrosion of Reinforced Steel in Concrete Slabs, Vol. 5, Calcium Nitrite Admixtures or Epoxy Coated Reinforced Bars as Corrosion Protective Systems, FHWA-RD-83-012, FHWA, US Department of Transportation, 71. 

Intake water tunnels are generally made from concrete, and absorption of water by concrete is the main reason for corrosion in reinforcement. In intake structures the problems are due to concrete failure from salts penetrating into the concrete and corroding the rebar. Hard, dense concrete with ample cover to reinforcement and without cracks and porosity has good resistance to corrosion against seawater. In Indian nuclear power plants, the experience with concrete intake tunnels with respect to corrosion behavior is not bad except that special care is required for protection against algae, clams, mussels, etc. which attach to the tunnel surface. 

P. Pedeferri, G. Mussinelli and M. Tettamanti, Experiences in anode materials and monitoring systems for cathodic protection of steel in concrete , in Corrosion of Reinforcement in Concrete, edited by C. L. Page, K. W. J.Treadaway and P. B. Bamforth, Elsevier Applied Science, London, UK, 1990, pp 498-506. 

McDonald, D.B., Sherman, M.R., Pfeifer, D.W., and Virmani, Y.P., Stainless Steel Reinforcing as Corrosion Protection, Nickel Development Institute, Reprint Series 14034, August 1995. 

All this testifies to the fact that the maximum effect is obtained with the use of polymer coating for strengthening of reinforced concrete beams and simultaneously for further corrosion protection. 

The neutralization of concrete leads to reduction of the corrosion protective function of concrete against reinforcing steel, and has an important influence on the durability of reinforced concrete structures. The neutralization is influenced by various factors (concentration of CO2 gas, type of concrete, water-to-cement ratio(W/C), water content, type of finishes and their thickness and permeability, temperature and humidity conditions, etc.). From the physicochemical point of view, this process can be considered to be the diffusion of CO2 inwards into concrete from the surface, accompanied by the conversion of Ca(0H)2 into CaC03. In this context, -unsteady state dynamics has been done for the progress of neutralization of concrete in order to rationally understand the process and the influence of finishes on the process (, . ... 

A. Mazzoni, E. Nolan, H. Wojtas, Reinforcement corrosion and concrete resistivity - State of the art, laboratory and field results , Proc. Int. Conf. on Corrosion and Corrosion Protection of Steel in Concrete,... 

The processes of deterioration of concrete and corrosion of reinforcement are closely connected (Figure 3.1). The former provoke destruction of the concrete cover or cause microcracking that compromises its protective characteristics. On... 

R. B. Polder, Cathodic protection of reinforced-concrete stmctures in the Netherlands — experience and developments , in Corrosion of Reinforcement in Concrete - Monitoring, Prevention and Rehabilitation, Papers from Eurocorr" 97, J. Mietz,... 

This chapter deals with the characteristics required of concrete so that corrosion of reinforcement is not likely throughout the service life. The techniques of additional protection that may be needed for particular conditions of a essiveness are also outlined in this chapter and will be illustrated in the following ones. 

Surface treatments are applied to new structures as a preventative measure, to existing structures where the need for future protection is anticipated, and to repaired structures in order to improve the service life of the repairs (as well as to mask the visible effect of repairs). Of the many types of surface treatment of concrete, only those aimed at providing protection against corrosion of reinforcement will be mentioned here. This places coatings for protection against chemical attack outside the present scope. 

Galvanized reinforcement offers significant advantages compared to carbon steel under equivalent circumstances. These include an increase of initiation time of corrosion a greater tolerance for low cover, e. g. in slender (architectural) elements, and corrosion protection is offered to the reinforcement prior to it being embedded in concrete. 

Epoxy coating of reinforcing bars is a protective technique developed in the 1970s in North America. Laboratory results confirmed the effectiveness of the epoxy-coated bars, in many cases, in preventing corrosion of reinforcement in carbonated or chloride-contaminated concrete [46]. Recently, however, doubts have arisen about their long-term durability in very aggressive environments, doubts borne out above all by negative experience reported on structures in tropical environments [47-49]. 

---