Dezincification Corrosion Research Articles

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.

Failure analysis of the condenser brass tube in 150 MW thermal power units

In this case study, the failure cause of a condenser brass tube in 150MW thermal power units was investigated. The features of erosion were observed by macro and micro observations, and the necessary conditions for erosion were satisfied: higher flow rate, turbulence and silts contained in cooling water. The dezincification–corrosion was also verified in this case study by EDS analysis. Given all of that, the failed condenser brass tube is considered to be caused by the synergism of erosion and dezincification–corrosion.

CORROSION BEHAVIOR OF COPPER ALLOYS IN DEEP OCEAN ENVIRONMENT OF SOUTH CHINA SEA

The corrosion in deep ocean environment has been paied more and more attentions to the exploitation of marine resources.Different from shallow marine environments,deep ocean environments are specially characterized by high hydrostatic pressure,low temperature,variable dissolved oxygen content and pH value in deep ocean,etc..So the corrosion behaviour of materials,such as ferrous and nonferrous metal and coatings,in deep ocean environments is different from that in shallow marine environments.A number of researches have been carried out to investigate the corrosion behaviour of metals in natural deep ocean in a few developed countries.Such researches,however,began until 2008 in South China Sea.In this work,the corrosion behavior of H62 brass,QA19-2 and QSn6.5-0.1 bronze in 800 and 1200 m deep ocean environments of South China Sea was studied using field tests.The results indicated that the corrosion rates of copper alloys decreased in the following order:H62(0.042 mm/a) QSn6.5-0.1(0.004-0.007 mm/a) QA19-2(0.003 mm/a).The corrosion rate of H62 brass decreased linearly with the increase in depth.While the corrosion rates of QA19-2 and QSn6.5-0.1 bronze decreased first and then increased with the increase in depth.The minimum value of corrosion rate occurred between 800-1200 m.The morphology and composition of corrosion products were investigated using SEM,EDS and XRD.The results demonstrated that the dezincification corrosion obeying solution-redeposition mechanism in H62 brass occurred.The corrosion products were composed of Cu,ZnO,Zn_5(OH)_8Cl_2H_2O and Cu(OH)_2H_2O.And the dealloying corrosion in QA19-2 and QSn6.5-0.1 bronze occurred.The corrosion products of QA19-2 bronze consistof Cu_2O and CuCl_2,and those of QSn6.5-0.1 bronze Cu_2O,CuCl_2 and Cu_2Cl(OH)_3.

Study on Corrosion Resistance of Al, Ni Brass with Processing State

The dezincification corrosion resistance of complex aluminum-brass HAl72-2.5-1 was studied by weight-loss, metallographic analysis method and energy dispersive spectroscopy. The effect of processing states and Al content（2.0%、2.5%、3.0%）in brass on zinc corrosion resistant was investigated. The research result shows that corrosion resistant is affected greatly by processing state, as-cast organization is loose and with much beta phrase, the dezincification of beta phrase is easy in corrosion solution, corroded at 75°C in 1% CuCl2 solution for 30 days. The dezincification layer of as-cast brass is over 137.3μm. Compare with the as-cast alloy, the corrosion depth of brass plate hot-rolled is only about 70.6μm, because the recrystallization process and the β phase dissolved into α phase during hot rolling process, the construction is more condense than that in as-cast state. The corrosion goes easily along the grains orientation which occurs in cold rolling, and existence of residual stress accelerates stress corrosion, which turns higher corrosion rate than that hot-rolled brass. The corrosion velocity enhances with the increase of Al content in brass.

Characteristics of Rich Phytic Passivator without Cr for Brass Strip

The surface of brass strip is easily oxidized to cause discoloration when exposed in the air. If it contacts with the electrolyte, there will be an electrochemical reaction in the surface that lead to increasing dezincification corrosion. To improve the anti-tarnish ability, the best method is to form a protective membrane in the strip surface. Phytic acid is easily formed a stable chelate complex compound with metal ions, so that forming a dense layer to protect brass strip. It is necessary to develop a new type surface passivator which rich in phytic acid and aquae hydrogenii dioxide but without Cr which pollutes the environment. The study results show that: This passivator enable the anti-tarnish capacity significantly, and do much better results and without so much pollution than now often used dichromate passivator. The passivator solution is stable and can use longer.

A study on the 65‐35 brass corrosion inhibitor

AbstractThe influence of new inhibitor namely 1,3‐bis‐diethylamino‐propan‐2‐ol (DEAP) on the dezincification corrosion of 65‐35 brass in simulated atmospheric water was studied by potentiostatic current transient measurement, solution analysis and surface evaluation techniques. Potentiostatic current transient results showed that the investigated inhibitor can effectively inhibit the chemical dissolution of brass in simulated atmospheric water. Solution analysis revealed that the weigh loss of brass electrode remarkably decreased in the presence of DEAP, changing from 7.375 × 10−3 mg (blank) to 9.567 × 10−4 mg (10−2 M). The scanning electron microscope (SEM) and electron probe microanalyzer (EPMA) measurements showed that DEAP may better adsorb to zinc component than to copper component, inhibiting the dezincification of brass in solution by a mixed complex film of Zn(II)‐DEAP and Cu(I)‐DEAP. The nature of the inhibited film was analyzed by an X‐ray photoelectron spectroscope (XPS) analyzer.

Review of Brass Dezincification Corrosion in Potable Water Systems

Review of Brass Dezincification Corrosion in Potable Water Systems

Failure analysis of cooling water pipes used in the condensation system of a gas turbine

The copper–zinc alloy pipes used in the condensed water system of a power plant failed within a period of 5 to 6 years. Because the service life of such a system was expected to be on the order of 20 years, an investigation was carried out to determine the possible causes for early failure of the pipes. Visual inspection revealed that the damage was generally in the form of holes. Further examination revealed that the pipes damaged over this relatively short period of time were constructed of copper–zinc alloys that are not resistant to dezincification corrosion.

鉛フリー快削性銅合金“75.5Cu-3Si-0.1P-Zn”の金属組織と耐脱亜鉛腐食性

We have developed a free-cutting copper alloy “75.5Cu-3Si-0.1P-Zn” free of lead which is known to be harmful to the human body. The microstructure of this developed alloy consists of α, κ and γ phases. The two hard κ and γ phases act as a source of stress at the time of cutting. As a result, the 75.5Cu-3Si-0.1P-Zn alloy is obtained in finely segmented chips with low cutting resistance. Incidentally, for plumbing fixtures such as cocks, vessels, valves, and joints related to the daily intake of tap water, copper alloys containing 2∼6 mass% lead are used. A switch to a lead-free material in the water supply system is urgently required. At the same time, accidents due to dezincification corrosion associated with water quality are frequently encountered in Japan, and there is a strong demand for materials with excellent dezincification corrosion resistance. In this study, we investigated the microstructure and dezincification corrosion resistance of the developed alloy by the ISO 6509 test method.Single-phase alloys of α, κ and γ phases were prepared by laboratory methods and their dezincification corrosion was evaluated. The α phase and κ phase each has excellent dezincification corrosion resistance and the γ phase also has good dezincification corrosion resistance. Therefore, the developed alloy consisting of these phases is believed to have excellent dezincification corrosion resistance.

Effects of microstructural factors and alloying elements on dezincification of brass.

From the viewpoint of ecomaterals, development of dezincification resistant Pb-less brass is required. In order to reveal the effects of microstructural factors and alloying elements on dezincification of (α+β) brass, the brasses with different β phase area ratio and mean grain size of α phase were prepared by melting pure Cu, Zn and alloying elements and then pouring into a metal mold with three different solidification rates. Dezincification corrosion of the casting brass was examined by means of galvanostatic anodic polarization test. The results show that the mean and maximum dezincification depths of Cu-Zn system decrease with the decrease of the mean grain size of α phase. However, reduction of the dezincification depth by only controlling the microstructural factors has a limitation. The dezincification can be retarded significantly by the addition of a small amount of P and the refinement of the mean grain size of α phase with controlling the solidification rate.

COPPER ALLOY No. C44400 and C44500

Abstract COPPER ALLOY NOS. C44400 and C44500 are copper-zinc-tin alloys inhibited by antimony and phosphorus, respectively. They are commonly known as inhibited admiralty metal or admiralty brass. They have a good combination of strength and ductility and good resistance to general corrosion. The small addition of inhibitor is made to minimize the alloy’s susceptibility to dezincification and stress corrosion. They are used for condenser, evaporator and heat-exchanger tubes and associated applications. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness and creep. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: CU-599. Producer or source: Copper and copper alloy mills.

COPPER ALLOY No. C44300

Abstract Copper Alloy No. C44300 is a copper-zinc-tin alloy inhibited by arsenic; it is commonly known as inhibited admiralty metal or admiralty brass. It has a good combination of strength and ductility and good resistance to general corrosion. The small addition of arsenic (nominally 0.06%) is made to minimize the alloy's susceptibility to dezincification and stress corrosion. It is used widely for condenser, evaporator and heat-exchanger tubes and associated applications. This datasheet provides information on composition, physical properties, microstructure, hardness, elasticity, and tensile properties as well as fracture toughness and creep. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Cu-526. Producer or source: Copper and copper alloy mills.

黄銅の脱亜鉛腐食

黄銅の脱亜鉛腐食