Diffusion mechanism of dezincification in double phase brass exposed to seawater

Zinc diffusion kinetics of double phase brass as they were corroded in seawater was investigated by means of metallography microscope and mathematics regression analysis. The results showed that, the dezincification corrosion of β phase continuous HMn58 2 brass is characterized by β phase volume diffusion, while that of α phase continuous HSn62 1 brass is controlled by α phase grain boundary diffusion. Apparent diffusion coefficients of zinc in both types alloys were calculated out by founding diffusion equation and boundary conditions. It was found that the value of theoretical calculation is close to that of experimentally measured, and it confirmed that Sn element inhibits dezincification of brass. The relativity between the dezincification depth and corrosion rate of different double phase brasses immersed in seawater was revealed. : Zinc diffusion kinetics of double phase brass as they were corroded in seawater was investigated by means of metallography microscope and mathematics regression analysis. The results showed that, the dezincification corrosion of β phase continuous HMn58 2 brass is characterized by β phase volume diffusion, while that of α phase continuous HSn62 1 brass is controlled by α phase grain boundary diffusion. Apparent diffusion coefficients of zinc in both types alloys were calculated out by founding diffusion equation and boundary conditions. It was found that the value of theoretical calculation is close to that of experimentally measured, and it confirmed that Sn element inhibits dezincification of brass. The relativity between the dezincification depth and corrosion rate of different double phase brasses immersed in seawater was revealed.

Effect of Hydrogen on Dezincification Layer-Induced Stress

The effect of hydrogen on the dezincification layer-induced stress and the susceptibility to SCC was investigated. Experimental results showed that the dezincification layer-induced stress increased with increasing hydrogen concentration, and 3x10-6 hydrogen could increase the susceptibility to SCC of brass in ammonia solution by 10%.

Combination of Dezincification Carbon Anhydrase with Dansylamide for Zinc Biosensing

This work demonstrated quantitatively that DSA （dansylamide） and apo CA （dezincified carbon anhydrase） interacted with each other in the presence of Zn2＋ （zinc ion）. The fluorescence emission of DSA in the presence of Zn2＋ and the intensity of fluorescence, which was proportional to the concentration of Zn2＋, could be used in the measurement of Zn2＋ concentration. Considering that Zn2＋ was the active center of enzymes like CA （carbon anhydrase）, two dezincification reagents were compared to ensure the validity of our method. A certain range concentration of Zn2＋ could be measured by the reaction product of apo CA, DSA and Zn2＋, where the measurement limitation was about 60 nmol/L. Interaction of CA with DSA was also studied with infrared spectrometry.

Study of Dezincification Corrosion Behavior of Brass Exposed to Seawater and Its Inhibition Mechanism

The Characteristic and mechanism of corrosion of brass exposed to seawater for several years, including alloys with single alpha-phase and alpha + beta phase, were investigated by means of metallograph, SEM, EDS and so on. It shows that severe corrosion with intergranular and dezincification characteristics occurred on the specimens of H-68A, which was single alpha-phase brass with As element addition. For the brass of HSn70-1A, which was single-phase alloy with ils and Sn additions, much better corrosion resistance could be exhibited due to the formation of Sn enrichment corrosion product film. Sn element is much easier to enrich at phase and grain boundaries than towards surface film. This would inhibit dezincification of the alpha + beta phase brass to some extent. However, it is not enough for the Sn element addition in the brass HSn62-1 with alpha + beta phase to resist dezincification corrosion getting through phase and grain boundaries of the brass. The alleging elements boundary diffusion plays an important role in the corrosion behavior of both alpha-phase and alpha + beta phase brass.

Synergistic mechanism of boron and arsenic in preventing dezincification of brass

IN the past, trace amount of arsenic was used to reduce the dezincification of brass, but in re-cent years, it was found that trace amount of boron also could prevent the dezincification ofbrass. By adding boron and arsenic alone or both, we found that boron or arsenic couldreduce the dezincification of brass, the synergistic effect of boron and arsenic in

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.

Numerical simulation of the direct reduction of pellets in a rotary hearth furnace for zinc-containing metallurgical dust treatment

A mathematical model was established to describe the direct reduction of pellets in a rotary hearth furnace （RHF）. In the model, heat transfer, mass transfer, and gas-solid chemical reactions were taken into account. The behaviors of iron metallization and dezincification were analyzed by the numerical method, which was validated by experimental data of the direct reduction of pellets in a Si-Mo furnace. The simulation results show that if the production targets of iron metallization and dezincification are up to 80% and 90%, respectively, the furnace temperature for high-temperature sections must be set higher than 1300~ C. Moreover, an undersupply of secondary air by 20% will lead to a decline in iron metallization rate of discharged pellets by 10% and a decrease in dezincing rate by 13%. In addition, if the residence time of pellets in the furnace is over 20 min, its further extension will hardly lead to an obvious increase in production indexes under the same furnace temperature curve.

Electrochemical behavior of Cu-Zn-Al shape memory alloy after surface modification by electroless plated Ni-P

The electrochemical behavior of Cu-Zn-Al shape memory alloy (SMA) with andwithout electroless plated Ni-P was investigated by electrochemical methods, in artificial Tyrode'ssolution. The results showed that Cu-Zn-Al SMA engendered dezincification corrosion in Tyrode'ssolution. The anodic active current densities as well as electrochemical dissolution sensitivity ofthe electroless plated Ni-P Cu-Zn-Al SMA increased with NaCl concentration rising, pH of solutiondecreasing and environmental temperature uprising. X-ray diffraction analysis indicated that aftersurface modification by electroless plated Ni-P, an amorphous plated film formed on the surface ofCu-Zn-Al SMA. This film can effectively isolate matrix metal from corrosion media and significantlyimprove the electrochemical property of Cu-Zn-Al SMA in artificial Tyrode's solution.