Corrosion behavior of brass coinage in synthetic sweat solution

Corrosion behavior of brass coinage was investigated in synthetic sweat solution by electrochemical measurement and surface analysis methods including scanning electron microscope （SEM） and energy dispersive X-ray spectrometer （EDX）. It is indicated that chloride ions in sweat solution accelerate the anodic active dissolution of brass, which is the main reason of pitting corrosion and dezincification corrosion. Meanwhile, lactic acid and ammonia water also promote the anode reaction. The corrosion products on the surface are mainly composed of basic copper chloride, cuprous oxide, the complex consisting of urea in association with copper, and few lactate ion. The kinetics of pitting corrosion development obeys the following equation of J0=0.3735（t＋185.93）^-1/2, and the process is controlled by dissolution of salt deposited on pit surface.

Effect of water chemistry on the hydro-mechanical behaviour of compacted mixtures of claystone and Na/Ca-bentonites for deep geological repositories

In the French deep geological disposal for radioactive wastes,compacted bentonite/claystone mixtures have been considered as possible sealing materials.After emplacement in place,such mixtures are hydrated by the site solution as well as the cement solution produced by the degradation of concrete.In this study,the effects of synthetic site solution and cement solution on the hydro-mechanical behaviour of compacted mixtures of claystone and two types of bentonites(MX80 Na-bentonite and Sardinia Cabentonite)were investigated by carrying out a series of swelling pressure,hydraulic conductivity and mercury intrusion porosimetry(MIP)tests.It was found that for the MX80 bentonite/claystone mixture hydrated with synthetic site solution,the swelling capacity was reduced compared to the case with deionised water owing to the transformation of Na-montmorillonite to multi-cation dominant montmorillonite by cation exchanges.For the Sardinia bentonite/claystone mixture,the similar increasing rate of swelling pressure was observed during the crystalline swelling process for different solutions,suggesting insignificant cation exchanges.Additionally,the cations in the synthetic site solution could reduce the thickness of diffuse double layer and the osmotic swelling for both MX80 bentonite/claystone and Sardinia bentonite/claystone mixtures.The large-pore volume increased consequently and enhanced water flow.In the cement solution,the hydroxide could also dissolve the montmorillonite,reducing the swelling pressure,and increase the large-pore volume,facilitating the water flow.Furthermore,the decrease of swelling pressure and the increase of hydraulic conductivity were more significant in the case of low dry density because of more intensive interaction between montmorillonite and hydroxide due to the high permeability.