Chloride Migration

R. E. Miller, F. P. Guengerich, Oxidation of Trichloroethylene by Liver Microsomal Cytochrome P450 Evidence for Chloride Migration in a Transition State not Involving Trichloroethylene Oxide , Biochemistry 1982, 21, 1090 - 1097. 

Ando, M. and Sayato, Y. Studies on vinyl chloride migrating into drinking water from polyvinyl chloride pipe and reaction between vinyl chloride and chlorine, Water Res., 18(3) 315-318, 1984. 

In this reaction a chloride migrates between silicon and the ammonium nitrogen, converting a zwitterionic hexacoordinate chelate (58) to a... 

Cationic surfactants and protonated polyamines may reverse the direction of the EOF as they impart a positive charge on the capillary wall. This technique is used to prevent wall interactions with cationic proteins. Changing the direction of the EOF is important in anion analysis where comigration of anions and the EOF is required. Otherwise, highly mobile anions such as chloride migrate toward the anode, whereas lower mobility anions are swept by the EOF toward the cathode. 

The next step is to test one or more of the selected concrete compositions using a compliance test that determines the chloride-penetration resistance. DuraCrete has adopted the rapid chloride migration (RCM) test for this purpose [21,25], which is a short-term test based on acceleration of chloride penetration by an electric field. 

J ci,o = chloride-penetration resistance determined from compHance tests (y/mm ), i. e. the inverse of the diffusion coefficient from the rapid chloride migration test (RCM),... 

M. Castellote, C. Andrade, C. Alonso, Changes in concrete pore-size distribution due to electrochemical chloride migration trials , ACI Materials Journal, 1999, 96-M39, May/)une, 314-319. 

In the case of highway bridges, the vast majority of the problems are caused by chloride migration into the concrete because of deicing salt application and marine exposure. On reaching the surface, the chloride ions cause the disruption of the passive film and create conditions favorable for accelerated corrosive attack on the... 

Pitting corrosion is initiated by chloride migration from the electrolyte to the metal-passive film interface. Chloride ions adsorb on the outer metal oxide surface, permeate and interact with the underlying metal [9,10]. Redox reaction at the interface increases... 

Keywords offshore wind energy, polymer-modified mortar, corrosion protection, durability, chloride migration, freeze-thaw... 

Rapid-Chloride-Migration test. The chlorides in sea water do not attack the mortar itself. However, exceeding the critical chloride content in the mortar near the steel surface might lead to a high corrosion risk. In that case, a localized corrosion occurs, which might spread quickly to the center of the steel tower. 

By adding polymer dispersions and thereby decreasing the permeability, a further reduction of the chloride migration coefficient can be achieved. The rapid chloride migration test is a quick tool to test the chloride resistance by applying a voltage [1]. In relation to the depth of cover, the risk for corrosion of the steel surface can be estimated in terms of time. 

The first test results after 28 days of storage under water already show a reduction of chloride migration coefficients for the mortars with polymer additives (Fig. 4). When compared to the reference mortar composition, a reduction in the chloride-migration-coefficient from 1.55x10-12 mVs to 0.80x10-12 mVs was achieved, by using styrene-acrylate of 20 % concentration. 

Therefore it can be summarized that the chloride migration resistance of the investigated mortars is also enhanced by adding polymer dispersions. 

Figure 4 Influence of polymer addition on the chloride-migration-coefficient...

The resistance of the concrete against chloride penetration was mainly tested by use of the Rapid Chloride Migration (RCM) method [6] and electrical resistivity measurements based on the two-electrode method [7], The testing was carried out on 50 mm cut slices from 0100 x 200 mm concrete cylinders, and the concrete samples were mainly cured in water with a temperature of 20 2 C and tested at regular intervals of up to 90 days. In addition, some samples from two of the concrete mixtures (PO O and Pl. O) were wrapped in plastic sheeting after demoulding and stored in air with a temperature of 20 2°C until time of testing. 

For all concrete samples used for the chloride migration testing, the results from the electrical resisitivity testing are shown in Table 6. Again, no beneficial effect of the hydrophobic agent could be observed for the water stored samples compared to that of the reference concrete (PO.O). For the concrete samples stored in air, however, (PO.OA, Pl. OA) intermixture of the hydrophobic agent clearly increased the electrical resistivity. 

NORDTEST NT Build 492. Concrete, Mortar and Cement Based Repair Materials Chloride Migration Coefficient from Non-Steady State Migration Experiments. Espoo (1999). 

Mechanism 3. Our last mechanism also involves a Te-Te-bonded intermediate, but it falls apart not via chloride migration but via aryl migration, as shown below ... 

Aluminum chloride/hydrogen chloride Migration of chlorine... 

The electrochemical reactions induce concentration gradients in the electrolyte present in the crack. When active dissolution takes place at the crack tip and oxygen is reduced further away or at the outside surface, the acidity of the electrolyte near the crack tip increases as a result of metal-ion hydrolysis. Electroneutrality requires that anions, such as chloride, migrate towards the crack tip to compensate the charge of the metal cations produced there. Both effects contribute to stabihze the active state of the crack tip. 

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