Korrosionsbeständigkeit von Verbindungen von Rohren aus nichtrostenden Stählen in Wässern

Corrosion of joints for stainless steel tubes in water The most important commonly used joining techniques for stainless steel tubes which are used for the transport of water and gases are welding and brazing. With corrosion attack by dry gases, both connections are resistant against corrosion. However, in water and aqueous condensates limits of application exist with regard to the corrosion resistance. The corrosion resistance of weld connections with stainless steel tubes is diminished by

• – annealing colours (oxide films) and scale layers in the weld area;
• – changes in the microstructure adjacent to the welds (sensitization of the stainless steel material);
• – surface finish of weld seams after welding;
• – welding faults resulting from bad handling and workmanship.

Type and extent of corrosion damage occurring on weld connections with decreased corrosion resistance depend on the composition of the water and condensates, mainly on their chloride content. Typical examples for the causes of degraded corrosion resistance of weld connections, and possible types of corrosion attack, namely pitting, crevice corrosion, and stress corrosion cracking and their mechanisms are described. Furthermore, measures are shown by which the corrosion resistance of weld connections with stainless steel tubes can be increased. Joints of stainless steel tubes by hard soldering with capillary fittings are endangered by knife line attack at the phase boundary between the stainless steel and solder (interfacial corrosion). Knife line attack means in this context the loss of adhesion between steel and hard solder. The severity of the corrosion risk, in particular the incubation time until the occurrence of the corrosion damage, depends on the water quality, mainly on chloride concentration, and pH. The press fitting with non-metallic gasket is a relatively new joining system, and it is used in the cold and warm water domestic installation. This joining technique is described. For domestic water distribution, an installation system with tubes and press fittings made of steel grade AISI 316 SS has been developed. This system is resistant to corrosion attack in potable water of usual composition, and it is already applied in-service in a considerable extent. Other joining systems are stainless steel weld fittings, threaded screw fittings, and compression couplings with cutting or clamping rings. They are used mainly in industrial installations.     

Die atmosphärische Korrosion von Kupfer und Bronze im Rahmen des UN/ECE-Expositionsprogramms. Zwischenbericht nach 4-jähriger Bewitterung

The atmospheric corrosion of copper and bronze within the UN/ECE Exposure Programme. Intermediate report after 4 years of exposure Accompanied by an extensive measuring programme for environmental data, copper (DIN 1787) and bronze samples (DIN 1705) were exposed at 39 test sites in 14 countries and examined afterwards. Measured were the weight change, the mass loss (after pickling of the corrosion products), the colour changes (trichromatic colorimetry), the chemical composition of the corrosion products (Debye-Scherrer), the layer thickness (eddy-current method), and the roughness of the weathered surface (perthometer). The corrosion data are related with the environmental data, especially the concentration of sulfur dioxide, the relative humidity and the conductivity of precipitations.     

Analysis of intergranular corrosion attack of stainless steels by means of atomic force microscopy and optical microscopy. Part 2: Influence of impurity content

The aim of this study is to compare different methods to quantify intergranular corrosion attack caused by impurity segregation in different austenitic stainless steels with varying impurity contents escpecially of sulfur. Therefore, the boiling nitric acid chromate test was used to produce the intergranular corrosion attack. The methods for quantification of these attacks were weight loss measurements and grooves depth measurements either by optical microscopy at cross sections or by AFM at topography images. Comparison of the results from the different methods show that with any method used the corrosion attack increases with increasing sulfur content. Grooves depth measurements by AFM is therefore an advantageous method to quantify changes to susceptibility to intergranular corrosion because of its high selectivity to grain boundary attack compared to the other methods.     

Die Bedeutung des Oxalsäure-Tests für die Prüfung der Korrosionsbeständigkeit nichtrostender Stähle

The meaning of the oxalic acid etch test for testing the corrosion resistance of stainless steels In the oxalic acid etch test according to ASTM A 262 practice A, precipitations of phases rich in chromium and molybdenum which can occur in stainless steels, are preferentially dissoved. The behaviour of such phases in the oxalic acid etch test was investigated taking precipitations of carbide M₂₃C₆, s?-phase, χ-phase and Laves-phase in stainless steels AISI 304 L and 316 L as examples. The chemical composition of these was evaluated with a scanning transmission electron microscope (STEM) by EDS. With coarser precipitations, it was possible to support this analytical method by EDS of metallographic cross sections in a scanning electron microscope (SEM). In oxalic acid, critical threshold potentials exist above which the above mentioned phases are preferably attacked, furthermore critical pH values, below which no selective attack of the precipitated carbides and intermetallic phases occurs. The numerical values of the threshold potentials as well as the critical pH values were evaluated. When testing stainless steels in the oxalic acid etch test, the steel specimens are polarized to a highly positive potential in the very trans passive range. In this potential range the corrosion rate of stainless steels increases with increasing chromium content, while in the active and passive range the corrosion rate decreases with increasing chromium content. Other than the nitric-hydrofluoric acid test, the copper-copper sulfate-sulfuric acid test, and the ferric sulfate-sulfuric acid test, the oxalic acid etch test does therefore not indicate any chromium depletion. Hence, an intergranular attack also occurs when precipitations of carbides rich in chromium are present at the grain boundaries of austenitic stainless steels with the carbides being precipitated without any chromium depletion of the areas adjacent to the grain boundaries. Sensitized austenitic stainless steels which are susceptible to intergranular corrosion due to the precipitation of chromium rich carbides and chromium depletion of the areas adjacent to the grain boundaries, can suffer intergranular SCC in high temperature aqueous environments when additionally critical conditions with respect to the mechanical stress level and the oxygen concentration in the environment are given. For the detection of sensitized microstructures, the oxalic acid etch test must be valued critically due to the dependence of the corrosion rate on the chromium content mentioned above, and is obviously by far less suited than the conventional tests for establishing resistance to intergranular corrosion in sulfuric acid-copper sulfate solutions with additions of metallic copper (Strauß test, severe Strauß test).     

Untersuchung der Potentialabhängigkeit der interkristallinen Korrosion eines sensibilisierten ferritischen Chromstahls mit rund 17% Cr

Investigations into the relationship between the potential and the inter-crystalline corrosion of a sensitized ferritic chromium steel with approx. 17 per cent, chromium Specimens of a ferritic chromium steel with 0.10 per cent. C and 17.43 per cent. Cr were used in order to ascertain, in the stable-annealed and sensitized condition, the relationship between the potential and the corrosion rate, polarisation current density and depth of penetration of the inter-crystalline corrosion attack. The tests were carried out in external potentiostatic arrangement over the potential range from E_H = + 250 mV to + 1250 mV in boiling 2 n H₂SO₄. All tests were extended over a standard period of 24 hours. Stable-annealed specimens showed no signs of corrosion attack whilst sensitized specimens showed inter-crystalline corrosion of the active-passive and passive-passive types. In the potential range of the active-passive type, the depth of penetration of the grain boundary attack decreases with increasing potential whilst, within the range of the passive-passive type, the depth is independent of the potential. The critical potential marking the boundary between active-passive and passive-passive corrosion is interpreted as the passivation potential of the zones with the greatest chromium deconcentration. With increasing sensitization, this boundary is shifted towards more positive potentials. The potential of the Strauss solution lies within the potential range most favourable for the test of the inner-crystalline corrosion of the active-passive type. The Strauss test in accordance with Steel-Iron Testing Standard 1875/61 is fully adequate for proving the grain decomposition resistance with non-stabilized 17 pC ferritic chromium steels.     

Analysis of intergranular corrosion attack on stainless steels by means of atomic force microscopy and optical microscopy. Part 1: Influence of heat treatment

The aim of this study is to quantify intergranular corrosion attack of heat treated low carbon austenitic stainless steel caused by segregation processes of P (0.2 at% P) by different methods. After nitric acid chromate test the intensity of intergranular corrosion attack was investigated by weight loss measurements as well as determination of depths of grooves by both the optical microscopy and AFM measurements. Generally, the largest attack of corrosion is noticed on samples heat treated at 550 °C. Results of weight loss include the corrosion of matrix, inhomogenities and grain boundaries. The depths of corrosion attack were determined by optical microscope on cross sections. This method can not distinguish between attacks at grain boundaries and attack of inhomogenities. Whereas, measurements of depths by line profiling of AFM‐surface images is related to grain boundary attack directly. The weight loss measurements as well as the optical microscopy and AFM‐measurements were compared for tested heat treatment conditions. It is concluded that the use of the AFM offers an advantageous method for quantifying intergranular attack.     

Klärung der Einzelmechanismen bei der Schädigung von Kupfer unter Kavitationsbeanspruchung in wäßrigen Medien

Study of the individual mechanisms giving rise to the destruction of copper under cavitation in aqueous media An experimental method developed by the authors enables the overall destruction mechanism during cacitation corrosion to be subdivided into the two main components “mechanical destruction” and “corrosion”. With the aid of impressed current it is then possible in a defined way largely to control the ratio of the two components of attack. Mechanical sollicitation due to the successive formation and collapse of bubbles in the liquid corresponds to the pattern found in corrosion fatigue; the authors have indeed found the phenomenological pattern of corrosion fatigue in some systems (grain boundary attack by electrochemical action, glide line attack by mechanical sollicitation).     

Angriff wäßriger Säuren auf Chemieemail

Attack of aqueous acids on chemical service glass enamel The acid attack on chemical service glass enamel (high resistant glass fused on to steel) is investigated at temperatures above the normal boiling point of the acid; the test procedure provides for conditions on a practical scale, i. e. high volume to surface ratios and short times of exposure. Testing is performed with an all-purpose tantalum lined autoclave and totally glass-lined steel samples which are evaluated gravimetrically. Thus the influence of many technically relevant parameters on the glass corrosion rate v₁ can be demonstrated: Volume to surface ratio V/O (v₁～e^?0/v), time of exposure (with and without renewal of the medium), temperature (v₁～e^?1/T), glass quality, type of acid, acid concentration, pressure, compressive stresses in enamel, agitation, influence of other ions and organic products, difference in liquid phase and condensate attack, dry steam attack. These quantitative detail results allow to determine in good approximation the corrosion situation of a glass-lined vessel under service analogue conditions. These new findings will also lead to more realistic view in rating the results of the test DIN 51 157 - ISO 2743.     

Korrosionselemente durch Gefügeheterogenität in nichtrostenden Chrom-Nickel-Stählen

Corrosion elements set up by structure heterogeneity in stainless chromium-nickel steels Transformation processes and precipitation of carbides could be the reason for corrosion elements in austenitic stainless steels. Examples are the intergranular corrosion and the selective martensite corrosion. The intergranular corrosion is based on a change of the electrochemical properties of the grain boundary regions by impoverishment of chromium. This “classical intergranular corrosion” takes place at all potentials. Resulting from the impoverishment of chromium after colling to very low temperatures, or by cold deformation, an α′-phase can be produced. This phase is only attacked in the active region of the current density-potential-curve. Both the intergranular corrosion and the corrosion of martensite are caused by local anodes. A selective attack of grain boundaries is also observed in the transpassive region. The intensity of this attack increase with precipitation of carbides. During the sensitivisation cathodes are produced, which cause a polarisation in the intergranular corrosive regions. Therefore, this attack of grain boundaries is not only connected with the formation of local anodes but also influenced by the formation of local cathodes.     

Einfluß des Molybdängehaltes niedriglegierter Stähle auf die Spannungsrißkorrosion in Nitratlösungen unter CERT-Belastung

Effect of molybdenum on the stress corrosion cracking behaviour of low alloy steels in nitrate solutions under slow strain rate testing conditions CERT tests ($ \mathop \varepsilon \limits^. = 10^{ - 6} {\rm s}^{ - {\rm 1}} $) were carried out in NaNO₃ solutions (0.1… 5 mol/l and 25… 90ßC) to determine the critical parameters for stress corrosion cracking. The steels tested were 15 Mo 3, LStE 36 and two laboratory heats with 0.08% C and molybdenum concentrations of 0 and 1%. All cracked specimens were examined metallographically. Different kinds of corrosion attack with and without intergranular features were observed. The critical potential range for intergranular attack is defined by two critical potentials. The negative critical potential is about U_H = ?0.2 V. It is hardly affected by the test parameters and the material. All free corrosion potentials lie in this range. All freely corroding specimens failed by intergranular cracking in 5 M NaNO₃ at 90°C. Only the coarse grained material without Mo showed intergranular cracks at even lower concentrations of NaNO₃. The positive critical potential varied widely over 0 to 0.5 V, depending on the test parameters and the material. Furthermore, in all cases a second critical potential range of intergranular attack was found at about U_H = 0.8 V. The potential range of U_H = 0.5 to 0.8 V for resistance against intergranular attack disappears with increasing temperature, as with the test conditions according to DIN 50 915 in boiling Ca(NO₃)₂ solutions. Furthermore, this was observed for the heat without Mo at already 90°C. With respect to environmental parameters, the effect of NaNO₃ concentration is very small but the effect of temperature is markedly high. The materials can be better characterized by critical temperatures rather than by critical potential ranges. Unified ranking of the materials with respect to their resistance to intergranular attack is not possible because of its dependence on the potential. However, on the basis of the extent of the domains in which the materials are resistant, it is possible to differentiate among the materials. Their resistance to intergranular attack increases in the following order: Heat without Mo → LStE 36 → 15 Mo 3 → heat with 1% Mo. The effect of Mo is explained in terms of its association with high proportions of bainite in the microstructure.     

用自腐蚀电位预测LY12CZ铝合金的腐蚀损伤

研究了ＬＹ１２ＣＺ铝合金在ＥＸＣＯ溶液中的自腐蚀电位和最大腐蚀深度随浸泡时间的变化关系。结果表明,ＬＹ１２ＣＺ铝合金在ＥＸＣＯ溶液中的腐蚀动力学可分为两个阶段,浸泡前期,腐蚀发展较快,但腐蚀动力学的规律性不明显;浸泡后期,腐蚀发展稍慢,腐蚀动力学近似地遵循线性规律。     

Mikrobielle Werkstoffzerstörung – Simulation,Schadensfälle und Gegenmaßnahmen: Untersuchung der Beständigkeit von keramischen Werkstoffen

Microbial deterioration of materials – simulation, case histories and countermeasures: Testing of the resistance of ceramic materials Testing of microbiologically influenced corrosion of ceramic materials by biogenic sulphuric and nitric acid corrosion is well described and applied for constantly moist buildings like sewage pipelines and cooling towers. The complex situation on historical buildings of natural sandstones has not yet been investigated in the laboratory. A double-chamber cabinet and a test system for the simulation of chemically (gaseous pollutants), combined chemically and microbiologically (gaseous pollutants plus nitrifying bacteria) and solely micro biologically (nitrifying bacteria) influenced corrosion of natural sandstone is presented. A high stone moisture was essential for the growth of nitrifying bacteria on test stones. Under optimum conditions a nitrifying biofilm developed on the calcareous Ihrlersteiner green sandstone, reducing the evaporation from the stone surface. Biofilm cells adapted well to high concentrations of gaseous pollutants (1,065 μg/m³ sulphur dioxide, 850 μg/m³ nitric oxide, and about 450 μg/m³ nitrogen dioxide): in the simulated smog atmosphere. The mean metabolic activities of ammonia oxidizers were 11 times and those of nitrite oxidizers 30 times higher than mean values of samples from historical buildings. The microbiologically, influenced nitric acid corrosion alone was 8 times stronger than the chemically influenced corrosion by the simulated smog atmosphere. If sulphur dioxide was added, the microbiologically produced nitrite was removed by chemodenitrification. Thus, the combined attack of nitrifying bacteria and gaseous pollutants did not result in an increased corrosion, but the nitrifying biofilm promoted the formation of gypsum.     

Einfluß der Elemente Phosphor,Mangan, Chrom,Molybdän und Vanadium auf das Verhalten niedriglegierter Stähle bei Spannungsrißkorrosion

Influence of elements such as phosphorus, manganese, chromium, molybdenum and vanadium on the stress corrosion behaviour of low alloy steels A series of such steels having graduated alloy addition contents were obtained experimentally in an electrical furnace and were tested under permanent tensile loads in calcium nitrate solution after different heat treatments and at different relative loads. The heat treatment has a very pronounced bearing on corrosion susceptibility: overheating produces the highest sensitivity annealing at 750°C the — relatively — highest resistance, while normalizing occupies an intermediate position. P has but little effect on corrosion susceptibility so that its influence can practically be neglected. Mn seems to have generally a beneficial effect while Cr — even in amounts up to 2% — is unable to improve corrosion resistance. In the case of V there is some improvement in some cases only while Mo generally produces increased corrosion resistance. In this connection, a new method for evaluating experimental results has been described, which has been developed for the practice of steel assessment. The experimental results confirm, that a steel may be designated ?resistant”? at a certain load when its useful life under tensile load in alkaline media is 240 hrs. Extension of the test duration does not yield an improvement in evaluation accuracy.     

Chloridinduzierte Korrosion von Nichtrostenden Stählen in Schwimmhallen-Atmosphären Teil 1: Elektrolyt Magnesium-Chlorid (30%)

Chloride induced corrosion on stainless steels at indoor swimming pools atmospheres Part 1: electrolyte magnesium-chloride (30%) The work was started on the occasion of failures of stainless steel components at the indoor swimming pool atmosphere in Uster (Switzerland). Highly-alloyed stainless steels were tested at defined mechanical and environmental conditions. Therefore U-bend specimens with salt spots were examined at 40°C and 35 and 70% rel. humidity respectively. A further test series was realised with round specimens under constant load in a stress cracking testing system at the same temperature and humidity conditions. The highly-nitrided steels 1.4529 and 1.4565 showed the best corrosion resistance. The steels 1.4401, 1.4462 and 1.4539 incured the highest corrosion attacks. Stress corrosion cracking (SCC) was determined at the steels 1.4401 and 1.4462 at 35% rel. humidity by metallographic structure micrography only. A distinctive relationship was observed between the pitting resistance equivalent and the kind of corrosion attack.     

Untersuchungen zum Einfluss des Stickstoffs auf das Lochkorrosionsverhalten hochlegierter austenitischer Cr‐Ni‐Mo‐Stähle

Investigation of the influence of nitrogen on the pitting corrosion of high alloyed austenitic Cr‐Ni‐Mo‐steels Austenitic stainless steels (18% Cr, 12% Ni, Mo gradation between 0.5 to 3.6%) had been gas‐nitrided. By stepwise removal, samples could be prepared with various surface content of nitrogen up to 0.45%. The susceptibility against pitting corrosion of these samples had been tested by two methods: – determination of the stable pitting potential in 0.5 M NaCl at 25°C – determination of the critical pitting temperature in artificial sea water (DIN 81249‐4) The influence of nitrogen to both determined parameter can be described well by PRE = Cr + 3,3 · Mo + 25 · N That means for the investigated steel composition and the used corrosion system there is no influence of molybdenum on the effectiveness of nitrogen.     

Lochkorrosionsverhalten von Auftragschweißungen – Schweißlagen‐ und Oberflächeneffekte –

Pitting corrosion behaviour of built‐up welds – Effects of welding layers and tarnish – The pitting corrosion resistance of nickel based deposition welds on a superduplex steel made by active‐gas metal pulsed‐arc welding was studied. Therefore the determination of the CPT (Critical Pitting Temperature) should be carried out corresponding to ASTM G 48 C. However an unexpectedly low resistance of the built‐up welds also at multilayer order was noticed. After visual assessment of the examined specimens a significant effect of the surface condition was assumed. Because the CPT determination according to ASTM does not allow any statement about the corrosion process, this method was not suitable to characterize the corrosion system. For this reason a new method was applied to clarify the causes of the low corrosion resistance. This method determines the CPT with the help of the electrochemical current noise under the same conditions demanded in ASTM G 48 C. The temperature is increased continuously and the characteristic parameters of the system are recorded and evaluated objectively within short time. So it was possible to see the influence of the surface condition on the pitting corrosion behaviour of the examined specimens. The required parameters to the post‐processing of the deposition welds were determined. The comparison of the results show that the surface tarnish formed after the shielded arc welding process influences the pitting corrosion resistance negatively. After its elimination the CPT could be determined in dependence of the welding layers.     

Korrosionsbedingte Veränderungen von Festigkeitseigenschaften metallischer Werkstoffe

Changes in the strength properties of metallic materials due to corrosion Corrosion produces changes in the strength properties of metals and such changes can be assessed by mechanicophysical testing of materials. The residual strength after corosion is proportional to the weight loss, e.g. for uniformly corroded copper and when the specimens are tested in the tensile ruptured. The elongation at break, however, shows an unexpectedly strong decrease already at low corrosion levels. In the case of intercrystalline corrosion the strength properties depend not only from the reduction of the load-bearing cross section, but, additionally, are determined by the notch effect of corroded grain boundaries. This fact is shown on potentiostatically precorroded specimens of a CrNi steel 18/9. At transpassive potentials this material is attached by intercrystalline corrosion even after solution annealing. Because oft he low intensity of the intercrystalline attack in this range of potentials there are, however, no significant differences in the strength behaviour of the steel after different sensibilization treatments. The fatigue resistance of the CrNi steel is becoming worse as intercrystalline corrosion is advancing into the depth of the metal structure. Chromium carbide precipitation have a favourable effect because they block slip planes and thus improve fatigue resistance.     

Besondere Aspekte der Temperaturführung und Wärmebehandlung hochlegierter Werkstoffe für den Chemie-Apparatebau

Special aspects of temperature control during heat treatment of high alloyed materials for the Chemical Industry High alloyed materials require a special control of the temperature during any annealing and fabrication procedure to assure the corrosion resistance, which was the main criterion for the selection of the material in the application proposed. Due to this requirement the time-temperature sensitization behaviour with respect to isothermal and polythermal heat treatments has been determined for alloy Cronifer 1925 hMo (1.4529), Nicrofer 3127 hMo (1.4562) as well as for the nickel base alloys Nicrofer 5716 hMoW (2.4819) and Nicrofer 5923 hMo (2.4605). The application of the standard corrosion test according to SEP 1877 II on alloys alloyed with at least 20% chromium shows no correlation between all second phase precipitation which can affect the corrosion resistance under practical conditions. For alloy Cronifer 1925 hMo and Nicrofer 3127 hMo the determination of the critical pitting temperature in the ferric chloride test has been shown to be an effective procedure to evaluate changes in the microstructure due to improper heat treatments during fabrication. The nickel based alloy Nicrofer 5716 hMoW, which is alloyed with only 16% chromium shows already high corrosion rates in the proper solution annealed and quenched condition, when tested according to the strong oxidizing test solution of ASTM G 28 A. Furthermore, the corrosion rate will increase rapidly after sensitization. Due to the fact that the alloy has not been developed for strong oxidizing media, the test media according to ASTM G 28 B should be applied, since it is more appropriate to this alloy. Although alloy Nicrofer 5923 hMo is alloyed with 23% chromium and 16% molybdenum the alloy exhibits a precipitation behaviour which allows easy fabrication of heavy components. Testing according to ASTM G 28 A allows the identification of improper heat treatments.     

Interkristalline,Kornflächen- und Spannungsriß-Korrosion von ausgehärteten AlZnMg 1-Legierungen

Intercrystalline corrosion, grain-phase corrosion and stress-corrosion cracking of aged AlZnMg1 alloys Potentiostatic polarisation curves and stress corrosion crack propagation of a pure and a commercial AlZnMg1-alloy, both peakhardened either by warm or by double ageing, were investigated in airsaturated sodium halide and sulfate solutions at a temperature of 303 K. For this, propagation of crack tips was observed microphotographically under potentiostatic conditions and under constant stress using specimens precracked by fatique corrosion. The pure alloy contents (weight percent): Zn 4,4; Mg 1,26; Fe 0,05; Si 0,006; balance Al, the commercial alloy: Zn 5,05; Mg 1,2; Fe 0,23; Si 0,1; Mn 0,23; Cr 0,2; Cr 0,2; Ti 0,074; Zr 0,12; Cu 0,056; balance Al. In sodium halide solutions either grain boundary and grain attack or only grain attack occurs at a potential region more positive than the respective breakdown potential. At the more negative restpotential no attack can be observed. The influence of concentration of chloride ions on the velocity of discontinuous crack propagation in the pure alloy, which starts without any initiation stage, is different for both heat treatments. No crack propagation is observed in the commercial alloy and in any case in sulfate solutions. The obtained stress corrosion cracking results may be explained by hydrogen embrittlement of the area around the crack tip.     

Moiré based method for real‐time crevice corrosion monitoring

A novel real‐time technique was developed to monitor localized corrosion occurring over a metal surface. It is an optical method based on the Moiré technique that has undergone further improvements and fine tuning for more accurate measurements. Upon testing, good agreements were obtained with the microscopically determined penetration depth. Application for this technique was demonstrated through real‐time monitoring of crevice corrosion activity occurring on the surface of AISI 316 (UNS S31600) stainless steel immersed in 3% NaCl at 60 °C. The crevice was an artificial clear glass/metal crevice with a gap thickness of 5 μm. Based on the findings of these results it was shown that this method can effectively and accurately be used to monitor crevice corrosion.