Zur Korrosion metallischer Werkstoffe in Tetrachlorkohlenstoff

Corrosion of metals in carbon tetrachloride Nickel, nickel alloys, titanium, the titanium-palladium alloy, carbon steel, stainless steel, zinc, aluminium und lead were immersed in the following boiling media: carbon tetrachloride dried and saturated with water and two phase mixtures of carbon tetrachloride and water. Titanium, the titanium alloy and nickel alloys of type C-4, G and 825 are high-corrosion-resistant, the alloy B-2 were only slightly corroded. Nickel, alloy 600, zinc and lead were corroded in the boiling two phase mixture. The weight loss of the stainless steel is very low, but the sensitivity of these steel grades to pitting and/or stress corrosion cracking have to be taken into account. Carbon steel and aluminium corroded heavily in contact with the boiling mixture. The composition of the gaseous phase corrosion products shows different corrosion mechanism.     

Kondensatorrohre aus Kupferwerkstoffen Richtlinien für Werkstoffauswahl und Betriebsbedingungen

Condenser tubes made of copper materials

• 1 Today, the copper alloys most generally used for condenser tubes are CuZn28Sn (Special brass 71 — Admiralty brass) CuZn20Al (Special brass 76 — Aluminium brass), as well as the copper-nickel alloys CuNi10Fe and CuNi30Fe. The high corrosion resistance of these materials is due to the electropositive normal potential of their base metal — copper — and to their ability to form a highly adhesive, protective sealing film. To counteract the dezinzification of copper-zinc condenser tube materials, alloying with arsenic or phosphorus is indispensable, and generally resorted to.
• 2 The properties of normal-type cooling waters and the phenomena of tube corrosion are discussed. In practice, the only difficulties are likely to arise if polluted waters are used. Especially at the time of commissioning, the tubes must be kept free of polluted water so as to ensure the formation of a dense and firm protective film.
• 3 The reaction of the tube material to the cooling water depends mainly on the p_H-value, on the carbonate, chloride and oxygen contents, and on the temperature and flow rate of the water.
• 4 The following practice rules are advised: For fresh water (containing less than 0.1 pC matter in dissolution) and flow rates exceeding 1.4 metres pr. second, tubes consisting of CuZn20Al or of a copper-nickel alloy should be used so as to avoid erosion-corrosion. If the sea water is greatly polluted, it is advisable — especially at flow rates around or above 3 metres pr. second — to use tubes consisting of CuNi10Fe or CuNi30Fe.

     

Effects of water vapour on isothermal oxidation of chromia-forming alloys in Ar/O2 and Ar/H2 atmospheres

Fe9Cr, Fe17Cr and Fe25Cr alloys were subjected to isothermal oxidation in Ar/O₂ and Ar/H₂ atmosphere at 700 °C as high temperature corrosion for 48 h. Oxidation weight change measurement showed increasing Cr content reduced the oxidation rate. The oxidized Cr alloys were analysed using SEM, TEM and XRD. The addition of water vapour accelerates the onset of breakaway oxidation kinetics for Fe9Cr. The presence of water vapour promotes internal oxidation of Cr within Fe9Cr. For Fe17Cr and Fe25Cr, the water vapour effect is not significant due to the large Cr reservoir due to continue growth of Cr₂O₃.     

Filiform corrosion of binary aluminium model alloys

The effect of alloy composition and microstructure on filiform corrosion (FFC) susceptibility was investigated for super-purity based binary model alloys of the systems Al-Mg, Al-Mn, Al-Fe and Al-Cu. Corrosion testing indicated that the presence of electrochemically noble second phase particles is a necessity for FFC to occur. Single phase, solid solution alloys of the Al-Mg, Al-Mn or Al-Fe systems did not support FFC. Heat treatment caused precipitation of the electrochemically noble intermetallic phase FeAl₃ in the Al-Fe alloy, resulting in extensive FFC. Precipitation of the phase MnAl₆, which has electrochemical properties similar to that of the aluminium rich matrix, by heat treatment did not impair the corrosion properties of the Al-Mn alloy. Significant surface oxidation and magnesium enrichment of the surface oxides by heat treatment did not affect the FFC properties of Al-Mg alloys. However, the solid solution binary Al-Cu alloys exhibited severe FFC. The detrimental effect of copper in solid solution is attributable to selective dissolution phenomena during the corrosion process, whereby copper was locally enriched on the surface as copper-rich particles providing efficient cathodic sites.     

Stress corrosion cracking and selective corrosion of copper-zinc alloys for the drinking water installation

Despite a generally good corrosion resistance to tap and industrial water, many brass taps and fittings have failed in the past by stress corrosion cracking (SCC) and selective corrosion (dezincification or preferred removal of a phase). The experimental investigations of the present study clarify the influence of the ammonia concentration on the two types of corrosion. Notched specimens made of the alloys CuZn39Pb3, CuZn40Pb2, CuZn37, CuZn36Pb2As and CuZn21Si3P are polarized anodically in pure tap water and tap water with realistic ammonia concentrations (15 and 30 ppm) under a simultaneous mechanical loading condition. The influence of stress and of the third alloying elements lead and arsenic are investigated and evaluated. The experiments show that the ammonia additions significantly increase the risk of dezincification of the α-β-brasses. The arsenic in the CuZn36Pb2As alloy avoids dezincification, but enhances the risk of SCC. The rate of selective corrosion and SCC consistently increases with increase in tensile stress.     

Untersuchungen zur Korrosion und zum Korrosionsschutz von meerwassergekühlten Rohrkondensatoren aus Kupferbasislegierungen-Versuche mit rotierenden Proben

Investigations on the corrosion and corrosion protection of seawater cooled condensor tubes of copper-base alloys - Experiments with rotating samples Experiments have been done on rotating disc and cylinder electrodes of CuZn20Al2, CuNi10Fe and CuNi30Fe in 3 w/o sodium chloride solution and in artificial sea water at 25 and 40 ° C. Erosion corrosion of sea water cooled tube condensors should be simulated and studied. The corrosion mechanism of copper base alloys in clean and polluted sea water was intensely studied with particular consideration to the influence of ammonia, sulfides and chlorine. The effectiveness of iron sulfate dosing was tested. With the rotating samples under test no erosion corrosion could be detected on free corroding specimens.     

Spannungsrißkorrosion an CuZn-Legierungen in sulfathaltigem Leitungswasser

Stress corrosion cracking of CuZn alloys in sulfate containing tap water Failure analyses of water-pipe fittings show inducing of stress corrosion cracking in α-brass by sulfates. In order to clarify this effect corrosion tests in 10% Na₂SO₄-solution and tap water were compared with results already published in literature.     

Die Abhängigkeit der Spannungskorrosionsanfälligkeit vom Werkstoffzustand bei homogenen Kupfer-Zink-Legierungen

Interdependence of stress corrosion susceptibility and structural state of homogeneous copper-zinc alloys Experimental investigations in ammoniacal solution of copper and ammonium sulfates have shown, that — with equal load ratio (σ/σ_0,2 = 0,9) — CuZn alloys are less sensitive to stress corrosion cracking after recrystallizing annealing than after cold working. The sensitivity increases with increasing Zn content and appears to depend primarily from the dislocation structure: parallel structures are highly sensitive while increasing transition to cellular dislocation structure reduces stress corrosion susceptibility. In the cold worked alloy the crack geometry is predominantly transcrystalline, in the recrystallized state intercrystalline. Similar relations between dislocation structure and susceptibility seem to exist in the case of austenitic stainless steels.     

The effect of iron on the corrosion characteristics of 90-10 cupro nickel in quiescent 3·4%NaCl solution

The corrosion resistance of 90-10 cupro nickel is very much dependent on small amounts of added Fe. It has been found that in quiescent 3·4%NaCl solution, corrosion rate decreases with increasing Fe and that both solutionized and precipitated Fe are effective. The corrosion product films were essentially similar in all alloys tested being mainly Cu₂O and Cu₂(OH)₃Cl. A complex Fe phase was identified on a 1·5wt.%Fe alloy which had undergone heat treatment to precipitate most of the Fe. A modification of the defect structure of Cu₂O increasing the electronic resistance of the corrosion product film is proposed as responsible for the increased corrosion resistance in cases where Fe is in solid solution. A complex Fe phase, which was found to have a high ionic resistance, was found responsible for the increased corrosion resistance of the precipitated alloy. The results are discussed with reference to current theories of corrosion product doping.     

Evaluation of corrosion behavior of Al-Mg-Li alloys in seawater

Weldalite 050, a high-strength Al-Mg-Li alloy, was evaluated for its corrosion resistance in deaerated and air saturated Arabian Gulf water to determine its suitability for marine applications. Weight loss and electrochemical studies showed that the alloy had minimum corrosion rates of 1.82 and 4.82 mpy (mils per year), respectively, in deaerated and air saturated Arabian Gulf water with very high total dissolved solids (TDS) content. Weldalite 050 exhibited good resistance to corrosion at velocities up to 3.9 m/s. The formation of Al₂MgLi, Al-Li, Al₁₂Mg₁₇, and Al-Li precipitates has a pronounced effect on its corrosion resistance. The corrosion resistance of Weldalite 050 compares favorably with that of alloys 5052 and 5054, wrought alloys 6061 and 6013, and silicon carbide (SiC) reinforced alloys 6061 and 6013.     

Microstructure and corrosion behaviour of ferritic steel–Zr-based metal waste form alloys in simulated ground water

ABSTRACT

The microstructure and corrosion behaviour of the metal waste form (MWF) alloys based on ferritic steel with Zr content in the range of 3–15?wt-% were investigated. The MWF alloys are composed of α-Fe and Fe-Zr phases and with the increase of Zr content, α-Fe phase gradually decreases and the relative content of Fe–Zr intermetallic phase also increases. TEM and XRD confirmed the presence of Fe₂Zr and Fe₂₃Zr₆ intermetallics. Potentiodynamic polarisation curves showed The MWF alloys exhibited passivation behaviour in the simulated Kalpakkam (KGW) and Rajasthan ground water (RGW) media. Electrochemical impedance spectra revealed improved passive film stability in RGW than in KGW which is related to the formation of more stable adherent insoluble passive film in RGW. Higher Zr containing MWF alloy exhibited higher corrosion resistance than lower Zr containing MWF alloys. The relative content of Fe–Zr intermetallics is attributed for the corrosion resistance of The MWF alloys.     

Die Korrosion von Kupfer-Aluminium-Legierungen in schwefelsaurer Beizlösung

Corrosion of copper-aluminium alloys in sulfuric acid containing pickling solutions Wrought copper aluminium alloys (aluminium contents between 5 and 10 weight-%, additions of Fe, Ni and Mn) have been studied by continous and alternating immersion tests in a solution containing 20% H₂SO₄ and 10% FeSO₄ at 40°C. In the as-extruded state the corrosion of monophasic alpha alloys increases with aluminium content. Larger quantities of ß' martensite exercise a negative effect. Addition of 2 weight-% Ni do not improve the corrosion resistance of the alloys with 5 and 8% Al. Cold reduction of alpha alloys give rise to a pronounced intensification of corrosion. No positive effect can be obtained by a thermal treatment of the alloys CuAl 10 Fe 4 Mn Ni and CuAl 10 Fe 4 Ni 5. The corrosion takes place under the following forms: uniform corrosion (CuAl 5), preferred corrosion of grain boundaries (CuAl*, Cual 9, Mn 2 FeNi and CuAl 10 Fe 4 Ni 5 after thermal treatment) and dealuminisation (CuAl 10 Fe 4 Mn 3 Ni). With a view to corrosion resistance the alloys CuAl 5, CuAl8 CuAl 9 Mn and - probably - CuAl 8 Fe seem to be superior to the others.     

Corrosion behaviour in salt spray and in 3.5% NaCl solution saturated with Mg(OH)2 of as-cast and solution heat-treated binary Mg–RE alloys: RE = Ce,La, Nd,Y, Gd

Corrosion behaviour was characterised in salt spray and in 3.5% NaCl solution saturated with Mg(OH)₂ of as-cast and solution heat-treated binary Mg–RE alloys. The corrosion rate in the immersion test for the solution heat-treated Mg–RE alloys was substantial, and was greater than that of high-purity Mg. These corrosion rates were probably caused by the particles in the microstructure and/or by Fe rich particles precipitated during the solution heat-treatment. The corrosion rate in the immersion tests for each as-cast Mg–RE alloy was greater than that of high-purity Mg, attributed to micro-galvanic acceleration caused by the second phase. Corrosion rates in salt spray had a general correlation with corrosion rates in the immersion tests, but there were differences. The values of apparent valence were always less than 2 consistent with Mg corrosion being only partly under electrochemical control.     

On the mechanism of high-temperature sulphur corrosion of binary alloys

Taking into account the phase composition and morphology of the scales three groups of alloys may be distinguished. The first of them contains alloys forming monophase scales which constitute solid solutions of sulphides of both alloy components (AgCu type). The mte of corrosion of these alloys is a monotonous function of their composition, and the mechanism of scale formation depends on the geometrical configuration of the reaction system. The second group includes alloys the components of which form sulphides of limited mutual solubility or sulphides having spinel structures (FeCr type); the scale may then be a mono- or double phase one and the exact structure is a function of the concentration of the alloying element. The metals belonging to the third group form mutually immiscible sulphides (CuZn type). The scales form double layers, the external layer being made up by sulphides of the base metal, while the internal layer is a heterophase mixture of the sulphides of both alloy components. The kinetics and the mechanism of the corrosion of these alloys is largely independent from the atmosphere (elemental sulphur or H₂? H₂S mixture).     

Untersuchungen zur Wirksamkeit des Natriumsalzes der 1-Hydroxyethan-1,1-diphosphonsäure als Inhibitor für Kupferwerkstoffe in Kühlwasser

Investigations on the efficiency of sodium salt of 1-hydroxyethan-1,1-diphosphonic acid as inhibitor for copper materials in cooling water The effect of sodium salt of 1-hydroxyethan-1,1-diphosphonic acid on the corrosion rates of copper, CuZn30, CuZn20A12 and CuNi10Fe1Mn in cooling water was investigated gravimetrically using a recirculating loop. In the presence of zinc ions sodium salt of 1-hydroxyethan-1,1-diphosphonic acid decreases corrosion rates. This phosphonate in connection with zinc salt is a promising inhibitor for CuZn20A12 in cooling water circulating systems.     

Cu元素对Al-Zn-Mg-Er-Sc-Zr合金组织演变和腐蚀性能的影响

利用Cu元素的含量变化研究了Al₈Cu₄Er相的形成与演变规律及其对Al-Zn-Mg-Er-Sc-Zr合金腐蚀性能的影响。结果表明：随着Cu含量的增加,合金晶粒得到显著细化,但同时固溶态合金不同类型的残余相增多;Al₈Cu₄Er相与Al-Fe相存在伴生关系,二者通过Cu与Fe交互作用实现相的转化,且可表述为如下关系式：;不同成分合金的晶间腐蚀均表现出与残余相密切相关的点蚀特征,含Cu、Er的Al-Fe相虽然具有更小的腐蚀坑尺寸,但网状分布特征使腐蚀深度有所增加;而具有更好耐蚀性能的Al₈Cu₄Er则因相的粗化和它与Al-Fe相的伴生关系导致合金耐蚀性能严重下降。     

Cu含量对铁基中熵合金耐腐蚀及抗菌性能的影响

采用水冷铜坩埚磁悬浮真空熔炼炉制备了(Fe_63.3Mn₁₄Si_9.1Cr_9.8C_3.8)_99.5?xCu_xAg_0.5 (x=1,2,3,4,5,at%)合金,并对合金试样进行抗菌时效处理,研究Cu含量对合金耐腐蚀性能以及抗菌性能的影响。结果表明,经过固溶时效处理后的中熵合金均为fcc结构,随着Cu含量的提高,fcc1富铁基体上逐渐析出了富Cu和富Ag的fcc2相。合金在3.5%（质量分数）NaCl溶液中的耐腐蚀性能优于AISI304。随Cu含量的增加,腐蚀电流密度先减小而后增加,容抗弧半径先增大后减小,表明合金的耐腐蚀性能先增强后减弱。合金在大肠杆菌悬浮液中的腐蚀速率呈现出先增大后减小的趋势,x=2合金的耐生物腐蚀能力最优,而抗菌性能和腐蚀性能存在倒置关系。富Cu和富Ag的fcc2相能有效提升合金的抗菌性能,x=5合金的抗菌性能最优,抗菌率达到99.94%.     

Modeling steel corrosion under supercritical CO2 conditions

Corrosion in the presence of CO₂ was studied under supercritical conditions (high pressure and moderate temperature) using different carbon steels and various corrosion resistant alloys (CRA's). An objective of this work was, among others, to put the results in perspective relative to various CO₂ corrosion models that have been developed and published over the years. In particular, the NORSOK, FREECORP, and OLI models were used for comparison, while others were discussed as well. The systems investigated were (a) supercritical CO₂ (SC CO₂) saturated with water (no separate water phase), (b) a water mist phase in equilibrium with SC CO₂, (c) a water/brine phase in equilibrium with SC CO₂. It was found that the OLI model best simulates the experimental corrosion rates observed in system (c) where coupons were corroded in the aqueous phase at high velocities in the rotating cage. The varying susceptibility of different carbon steels to corrosion under these conditions is highlighted. CRA steels are comparatively more resistant.     

Zum Einfluß von Chloracetylchloriden und Chloressigsäuren auf die Korrosion metallischer Werkstoffe in Trichlorethylen und Perchlorethylen

The influence of chloroacetyl chlorides and chloroacetic acids on the corrosion of metals in trichloroethylene and tetrachloroethylene The corrosive behaviour of selected stainless steels, nickel, copper and zinc materials in trichloroethylene and tetrachloroethylene containing dichloroacetic acid and dichloroacetyl chloride or trichloroacetic acid and trichloroacetyl chloride in concentrations between 100 and 10000 ppm from room temperature to the boiling point was investigated. NiCu 30 Fe was resistant in all systems investigated. Only tetrachloroethylene containing trichloroacetyl chloride corroded the stainless steels. Corrosion rates up to 0.07 mm/y and a tendency towards pitting corrosion were detected. Trichloroethylene containing dichloroacetic acid proofed aggressive towards Cu-DHP, CuZn 15, and CuSn 6. Corrosion rates between 0.14 and 0.32 mm/y were observed. Tetrachloroethylene containing trichloroacetic acid was far less corrosive towards copper materials. In tetrachloroethylene, containing trichloroacetyl chloride, of the copper materials investigated, CuZn 15 and CuAl8 were relatively strongly attacked (corrosion rate 0.10 mm/y). Of the investigated materials, Zn 99.95 was the least resistant to corrosion. Solutions containing acids and acid chlorides proofed to be the most aggressive with corrosion rates between 0.56 and 0.66 mm/y. Some corrosion products, developed on the metal surfaces, were analysed.     

Einfluß einer Eisenaufmischung auf das Korrosionsverhalten von NiCu30 Fe-Stahlplattierungen

The influence of iron pick-up on the corrosion properties of NiCu30Fe/steel clad materials The influence of iron pick-up on the corrosion properties of overlay and butt weldings of NiCu30Fe/steel cald materials was investigated by electrochemical tests in aerated artificial sea water (ASTM Standard D 1141-75) at 25, 50 und 80°C and by exposure to sea water in a sea water test rig on Helgoland. NiCu30Fe plates with defined Fe contents between 0% and 14% were used for comparison. On the Fe being distributed homogeneously, no negative influence of the iron on the pitting resistance was noted in aerated artifical sea water of 25°C up to an Fe content of 10%. The pitting resistance increases with rising temperature (50 and 80°C) and the Fe influence increases slightly. On exposure to sea water on Helgoland, the corrosion in the subtidal zone is mainly caused by marine growth resulting in the formation of shallow pits. In the tidal zone, Fe contents of more than 6.7% cause rust pittings at very low integral corrosion rates (≤0.002 mm/a). With integral Fe contents of between 0.5% and 3% in the final pass, the overlay welds have the same good corrosion resistance properties as commercial NiCu30Fe plate material. The compound butt welds exhibit slight pitting in the weld metal and the heat-affected zone which cannot be conclusively attributed to Fe pick-up but is rather due to the different free corrosion potentials of the NiCu30Mn(Ti) weld metal and the NiCu30Fe cladding material. In the tidal zone which is the preferential application of NiCu30Fe corrosion rates are less than 0.01 mm/a for all specimens welded by different welding methods. Iron contents of up to 8% which can be met by all welding methods when welded in two layers have no negative effect on the corrosion properties.