Search

SummaryThe occurrence of fingerprint and general corrosion on HE9 extrusions has been investigated. This form of corrosion can take place very rapidly and is shown up when the sections are etched and anodized. The presence of a magnesia-rich oxide film on air-quenched HE9 extrusions has been demonstrated; in order to establish the effect of this, air quenched sections having a magnesia film on the surface have been exposed at four different factory sites, together with sections from which the magnesia film has been removed by water quenching or acid dipping. The results show that these forms of localised corrosion can be directly attributed to the presence of a magnesia-rich film, and mechanisms by which attack is taking place are suggested.

Two established theories of SO2/atmospheric corrosion of iron, viz. the Acid Regeneration Cycle and an electrochemical model, are reviewed in terms of recently reported experimental results and acceptance of the electrochemical model as the main corrosion path. Theoretical analyses of proposed electrochemical mechanism are discussed and applied to a previously suggested mechanism, and a new one suggested here as an extension of recently reported results. Analyse einiger fur die atmospharische Korrosion von Eisen in Gegenwart von SO2 vorgeschlagener Mechanismen Die geltenden Theorien der atmospharischen Korrosion von Eisen in Gegenwart von Schwefeldioxid - namlich der Saure-Regenerationszyklus und ein elektrochemisches Modell - werden aufgrund neuerer experimenteller Ergebnisse uberpruft. Dabei wird gezeigt, das zwischen diesen neuen Ergebnissen und der Annahme des elektrochemischen Modells als des wichtigsten Korrosionsmechanismus kein Widerspruch entsteht. Theoretische Analysen der vorgeschlagenen elektrochemischen Mechanismen werden erortert und die Ergebnisse auf einen fruher vorgeschlagenen Mechanismus sowie auf einen neuen Mechanismus angewandt, der hier als Erweiterung aufgrund der neueren Ergebnisse vorgeschlagen wird.

A study of corrosion in tropical marine locations is of interest since high corrosion rates are expected to be obtained at such locations. Investigations made at Mandapam Camp, a tropical marine location on the south-east coast of India, show that the rates of corrosion of steel and other metals are exceptionally high and increase with duration of exposure at this site. Attempt has been made to relate the corrosion behaviour to meteorological factors and atmospheric salinity. Determinations have been made under various exposure conditions; at different distances from sea, at different angles of exposure, at different heights from the ground and by carrying out exposure during day and night separately and on upward and downward facing surfaces.

Bericht uber die atmospharische Korrosionsbestandigkeit zahlreicher Ni-haltiger Legierungen, die 13 und/oder 23 jahrelang der Industrieatmosphare von Bayonne, New Jersey, sowie 13 undloder 15 Jahre der Meeresluft von Kure Beach, Nord Carolina, in offenen und uberdachten Standen ausgesetzt waren. Untersucht wurden: Handelsubliches Nickel, NiCu-und NiCr-Leg., ausscheidungshartbare nichtrostende Stahle, NiFe-Knetlegierungen, Ni-haltiger Graugus sowie Legierungen die auf Grund ihrer spezifischen Ausdehnungserscheinungen eingesetzt werden, uber deren atmospharisches Korrosionsverhalten bisher aber noch nicht berichtet wurde. Masstabe zur Beurteilung des Korrosionsverhaltens waren: die Korrosionsgeschwindigkeit durch Messung des Gewichtsverlustes und Veranderungen des Oberflachenaussehens. Investigations into the atmospheric corrosion behaviour of some nickel alloys The authors report on the atmospheric corrosion resistance of numerous nickel alloys 23 years to the industrial atmosphere of Bayonne, New Jersey, and to 13 and/or 15 years to the marine atmosphere of Kure Beach, North Carolina, on open or covered stands. The metals covered by the research programme were commercial nickel, nickel-copper and nickel-chromium alloys, stainless steels suitable for dispersion hardening, ferronickel wrought alloys, with special expansion properties about which no reports concerning their atmospheric corrosion resistance had been published before. The criteria adopted for judging the corrosion resistance were the corrosion rate, measured as weight loss, and changes in the appearence of the surface.

The following article concerns an apparatus constructed to study the basic principles of atmospheric corrosion both under laboratory conditions and for open‐air tests. Written by workers at the Institute of Physical Chemistry of the U.S.S.R. Academy of Sciences and the I. V. Stalin Steel Institute, it has been translated from the Russian by Aluminium Laboratories Ltd., of Banbury.

三種の50キロ級厚板耐候性高張力鋼板を用いて四型式のy開先拘束割れ試験を実施し,主にルート割れについて検討した結果以下のような結論を得た.(1)拘束割れ試験片の拘束係数K0は,試験片の拘束状態で定まる修正係数aとスリット部の長さおよびそこで溶接部のしめる位置などで定まる無限板での拘束係数Kとの積K0=a・Kで求められるということが明らかとなった.この式によって本実験における各形式の試験片の拘束係数を求あてみると,JIS Z 3158試験片(S型)がはるかに大きく2スリット式の鉄研割れ試験片より小型のもの(K型),鉄研式割れ試験片(T型),S型試験片より拘束ビード部の短かい試験片(SS型)と順次小さくなるということがほぼ定量的に明らかとなり,各鋼材の割れ発生の限界拘束度が求められた.またこの限界拘束度曲線からルート割れ発生温度RT0は,ある範囲内(本実験では拘束度

A survey (is presented) of the work of the Corrosion Research Section of Chemical Research Laboratory (Department of Scientific and Industrial Research), Teddington, since 1939. The topics discussed include the “high-speed rotor apparatus” for accelerated immersed corrosion tests; the investigation of high-duty coatings; antifreeze solutions; corrosion inhibitors for use in heat-exchange systems, de-icing systems, wrapping materials, enclosed air spaces; accelerated atmospheric corrosion tests; methods of pre-treatment; bituminous coatings; microbiological (soil) corrosion; miscellaneous investigations and information services.

In einer Gemeinschaftsuntersuchung wird das Verhalten nichtrostender Stable an der Atmosphare gepruft. Proben mit 4 verschiedenen Oberflachenausfuhrungen der Stahle 1.4016 (17% Cr), 1.4301 (18% Cr, 9% Ni) und 1.4401 (18% Cr, 10% Ni, 2% Mo) wurden auf Versuchsstanden in Munchen, Frankfurt, Dusseldorf, Essen und Cuxhaven ausgelegt. Als Ergebnis nach einem Jahr Auslagerung bei unterschiedlichem Reinigungsaufwand wird festgestellt: 17%iger Cr-Stab1 ist fur Ausenatmospharen nicht ausreichend korrosionsbestandig;. 18/10/2-CrNiMo-Stahl war an allen Platzen vollkommen bestandig. In landlicher und in normaler Stadtatmosphare (Munchen, Frankfurt) ist 18/8 CrNi-Stahl ausreichend bestandig, dagegen ist bei diesem Stahl in Industrieatmosphare (Essen) eine regelmasige Reinigung erforderlich. Besonders in verschmutzter Industrieatmosphare macht sich eine glattere Oberflache (mattpoliert oder elektropoliert) gunstig bemerkbar. The corrosion resistance of stainless steels exposed to the atmosphere. Experience in Germany In a joint investigation, the behaviour of stainless steel exposed to atmospheric corrosion has been examined. Specimens with four different surface treatments of steels 1.4016 (17 pC chromium), 1.4301 (18pC Cr, 9pC Ni), and 1.4401 (l8pC Cr, 10 pC Ni, 2 pC Mo) have been exposed on test stands at Munich, Frankfurt, Dusseldorf, Essen and Cuxhaven. After one year of exposure, and applying different degrees of cleansing, the results can be summed up as follows: The corrosion resistance of 17 pC Cr steel is not adequate for atmospheric corrosion. The corrosion resistance of 18/10/2 Cr-Ni-Mo steel was satisfactory everywhere. 18/8 CrNi steel has an adequate corrosion resistance in rural and normal urban atmospheres (Munich, Frankfurt); in an industrial atmosphere (Essen), regular cleaning is essential. A smoother surface (matt polished or electro-polished) has a beneficial effect, especially in polluted industrial atmosphere.

Insgesamt 19 Baustahle wurden in Stadt-, Land- und Industrieatmosphare bis zu 3 Jahre lang exponiert. Die Auswertung der zu verschiedenen Zwischenzeiten bestimmten Gewichtsverluste ermoglichte die Aufstellung einer linearen Beziehung, mit welcher sich — innerhalb bestimmter Konzentrationsgrenzen — der Einflus einzelner Legierungszusatze feststellen last. Bei den Versuchen wurde gefunden, das die Wirkung der einzelnen Zusatze je nach Atmosphare und Korrosionsstadium verschieden ist und sich sogar von gunstig nach ungunstig verschieben kann; hierbei spielen auch Mengenverhaltnisse zwischen bestimmten Komponenten eine Rolle. Entscheidend fur das Korrosionsverhalten der Stahle sind durchweg P, S, Cu sowie daneben C und Mn. The influence of the chemical composition on the kinetics of the atmospheric corrosion of steel A total of 19 different structural steels were exposed to urban, rural and industrial atmospheres for periods up to three years. The evaluation of the weight losses determind at certain intervals permitted the establishment of a linear relationship which can be used for assessing, within certain limits of concentration, the influence of specific alloying elements. The tests showed that the effects of the different alloys varies with the type of atmosphere and with the degree of corrosion, and may well shift from “favourable” to “detrimental”. The results are also influenced by the quantitative ratios of certain components. The corrosion behavior of the steels is consistently governed by P, S and Cu and, to a lesser extent, by C and Mn.

Principles under which atmospheric corrosion tests are made are much the same as those applicable to other types of testing. Considered, among other things are, uses of accelerated tests, specimen size, location of test sites, differences in atmospheres, differences in metals and influence of alloying constituents. Mounting procedures, shape of specimens, drainage, influence of rainfall, influence of climatic variations, uses of shelters, reproducibility, test duration, evaluation of results. 2.2.2

Loss of chromium during steel mill processing is discussed together with the effect of this chromium depleted surface on atmospheric corrosion. A bench test for rapidly identifying the presence of chromium depleted surface is described and correlated with outdoor exposure tests. From laboratory studies cited several methods of overcoming this chromium depleted condition in Type 430 stainless steel are apparent. These methods include the use of a longer annealing cycle, a more complete pickling treatment alter each high speed anneal, and mechanical abrasion of the surface. 8.8.5

Es werden Passivierungslosungen fur feuerverzinntes und elektrolytisch verzinntes Weisblech zum Schutz gegen den Angriff von Schwefelverbindungen (Nahrungsmittel) Oxydation beim Erwarmen und gegen die atmospharische Korrosion untersucht. Verwendet wurden 0,1 bis 5 %ige Losungen von Kaliumpermanganat, Kaliumdichromat und verdunnte Schwefelsaure mit Zusatzen von Chromaten und Inhibitoren. Die Chromatlosungen zeigten nur dann eine gunstige Wirkung, wenn noch Zusatze gemacht wurden. Verzinnte Bleche, die so behandelt wurden, hielten einen mehrstundigen Angriff durch heises schwefelwasserstoffhaltiges Wasser stand, ohne sich zu verfarben und ohne das von den Poren aus eine Korrosion stattfand. Auch eine Erwarmung der behandelten Bleche bis auf 200° C fuhrte zu keiner Oxydation. The Passivating of Tin-plate Passivating solutions are examined for hot-dipped and electrolytically coated tin-plate for the protection against sulphur compounds (food), oxydation in heating and against atmospheric corrosion. Solutions of 0,1–5% of potassium permanganate, potassium dichromate and diluted sulphuric acid with additons of chromate and inhibitors have been employed. The solutions of chromate had a favourable effect only when additons of wetting mediums or phosphates were made. Tin-plate thus treated were resistant for several hours against hot water containing hydrogen sulphide without discolouring and without corrosion starting from the pores. Even the heating of the treated tin-plate up to a temperature of 200° C did not result in any oxydation.

The electrochemical theory of corrosion, by which the corrosion of steels, in solutions is readily explained, also is used to explain the start of atmospheric corrosion on ferrous surfaces...

Author explains in detail the kinetics of corrosion processes and gives a thorough study of their thermodynamical problems. He points out the factors which have influence on electrochemical corrosion. He investigates the role of cathodic inclusions concerning corrosion process in alloys and at the same time emphasizes their practical importance. He examines the corrosion processes taking place in the metals' passive state. Further, he describes the circumstances of the metals becoming transpassivated. Author sets up the electrochemical mechanism of soil corrosion of metals and points out the factors influencing soil corrosion. He also describes various cases of atmospheric corrosion, which can also be regarded as a sort of electrochemical corrosion. Finally, he investigates certain cases of corrosion taking place in melted metals. Author also gives a rational classification of corrosion control methods based on the electrochemical theory.

Werkstoffe aus Kupfer und Kupferlegierungen unterliegen bei ihrem praktischen Gebrauch der atmospharischen Korrosion. Die an der Ausenatmosphare entstehenden Korrosionsprodukte bilden vielfach auf der Werkstoffoberflache eine festhaftende farbige Schutzschicht. Am bekanntesten ist die grune „Patina” bei Dachbedeckungen und dgl. Hierdurch unterscheiden sich Kupfer und Kupferlegierungen von allen ubrigen Gebrauchsmetallen, denn bei keinem anderen Metall werden grungefarbte Schichten erhalten, die z. B. in der Architektur erwunscht und verwertet werden. An der Innenatmosphare bilden sich unter normalen Bedingungen von Kupfer und Kupferlegierungen korrosionshemmende Kupferoxid-Anlaufschichten. Auch diese Eigenschaft wird in der Technik verwertet. Die Art, chemische Zusammensetzung, Struktur, Schichtdicke, Dichte, Haftvermogen und die weiteren Eigenschaften derartiger Schichten aus Korrosionsprodukten hangen wesentlich von ihren Entstehungsbedingungen auf dem jeweiligen Grundwerkstoff ab. Bei der besonderen praktischen und theoretischen Bedeutung der hiermit verbundenen Probleme liegen umfangreiche Angaben aus dem Schriftum und aus praktischen Erfahrungen vor. Uber Einzelheiten und den derzeitigen Stand der Kenntnisse auf diesem Gebietȩ insbesondere uber die Bildungsgeschwindigkeit der Schichten in Abhangigkeit des Gehaltes der Atmosphare an Feuchtigkeit, Schwefelverbindungen, Chloriden, Nitraten Kohlensaure usw. wird berichtet. The atmospheric corrosion of copper and copper alloys Materials consisting of copper and copper alloys are, in their practical applications, exposed to atmospheric corrosion. In many cases, the corrosion products arising at the external atmosphere form, on the surface of the material, a coloured adhesive layer which protects the material. Best known is the green “patina” on roofs, etc. It is this feature which distinguishes copper and copper alloys from all other consumer metals since no other metal occasions green layers which are, e. g. as an architectural feature, regarded as desirable. As far as the indoor atmosphere is concerned, copper and copper alloys form, under normal conditions, corrosioninhibiting copper oxide films. This property, too, is made use of for technological purposes. Type, chemical composition, structure, thickness, density, adhesive power and other properties of such layers formed by corrosion products mainly depend on the circumstances under which the films appeared on the base material. In view of tbe special practical and theoretical importance of the problems associated with this phenomenon, a good deal of data are available in technical literature and from practical experience. The author deals with certain details and with the present state of knowledge in this sphere, especially in regard to the formation rate of the layers as a function of the contents, in the atmosphere, of moisture, sulphur compounds, chlorides, nitrates, carbonic acid, etc.

Auf Grund einer Analyse der elektrochemischen Reaktionen der atmospharischen Korrosion, des Entstehungsmechanismus ihrer festen Korrosionsprodukte und deren Eigenschaften folgt, das fur den langzeitigen Verlauf des Vorganges der Entstehungsmechanismus und die Eigenschaften der Korrosionsprodukte ausschlaggebend sind. Besonders betont wird die Bindungsform des Korrosionsstimulators (z. B. SO2) in den Korrosionsprodukten, ihre Wasseraufnahmefahigkeit, wobei der Zusammenhang beider Faktoren erortert wird. Der langzeitige Verlauf der atmospharischen Korrosion wird in folgende Teilvorgange gegliedert – Bildung einer Elektrolytschicht, Zerstorung der primaren Oxydschicht, Entstehung fester Korrosionsprodukte, Korrosion bei bestehender Schicht von Korrosionsprodukten. Dabei wird besonders die Korrosion bei bestehender Korrosionsproduktschicht als fur den langzeitigen Verlauf des Vorganges bestimmend betrachtet und vom Standpunkt eines stationaren Zustandes besprochen. Dieser Zustand wird vor allem von den Eigenschaften der Korrosionsprodukte beeinflust. Die praktische Anwendungsfahigkeit dieser Auffassung wird an drei Beispielen gezeigt – der Erhohung der Korrosionsbestandigkeit von Kohlenstoffstahlen durch Legieren, des Korrosionsschutzes verrosteter Stahloberflachen und beim Entwurf von Laborprufmethoden. Wege zur quantitativen Erfassung des langzeitigen Verlaufs der atmospharischen Metallkorrosion werden angedeutet. The influence of corrosion products upon the long-therm progress of atmospheric corrosion An analysis of the electrochemical reaction involved in atmospheric corrosion, and of the solid corrosion products and their properties reveals that the longterm progress of atmospheric corrosion depends from the mechanism of formation and from the properties of the corrosion products. Particular emphasis is placed upon the bonding type of the corrosion stimulator (e.g. SO2) in the corrosion products, and upon their water absorption capacity; the relation between these two factors is discussed. The longterm progress of atmospheric corrosion is divided into the following partial steps: formation of an electrolyte layer, destruction of the primary oxide layer, formation of solid corrosion products, corrosion in the presence of a layer of solid corrosion products. It is this latter step that is considered to be the step determining the mechanism of longterm corrosion; this step is discussed on the assumption of being a stationary state. This state is influenced in a first line by the properties of the corrosion products. The practical application of this view is demonstrated on three examples: increasing the corrosion resistance of carbon steels by alloying, corrosion protection of rust-covered steel surfaces, elaboration of laboratory testing methods. Some ways are pointed out which might enable a quantitative evaluation of the longterm mechanism of metallic corrosion in the atmosphere.

Three low alloy steels and an ordinary carbon steel were investigated as to the distribution of the alloy elements (Cu, Cr, P, Ni) in rust coverings produced either by weathering or by slight anodic oxidation. Electron microprobe examinations of rusts showed, besides an overall enrichment in the alloy elements, the presence of sharp concentration peaks in layers some ten μm wide. The more resistant the steel to atmospheric corrosion, the higher the rust to steel concentration gradient and the closer the concentration peaks to the steel/rust interface. Corrosion potential and polarization measurements in 0.1 M Na2SO4 on rusted specimens evidenced a marked effect of the interfacial enrichment in increasing the anodic polarizability and the tendency to a coverage passivation. This leads to looking upon the corrosion generated steel/rust interface as directly contributing, in addition to the rust itself, to the self protection of low alloy steels during atmospheric corrosion.

Meteorological and pollution data related to exposure trials should be collected with the specific aim of the corrosion tests clearly in view. The correlation between environmental data and corrosion kinetics may be approached either empincally or theoretically. Examples of both are cIted and discussed. Interactions between the environmental variables are important and equilibrium between the corroding surface and its environment must not be assumed. The most important factors to measure in studies of bare metals or metal cotaing are at present believed to be sulphur pollution chlorides, pH of rain, metal temperature and duration of wetness. the vanation of each with time must be recorded if interactions are to be adequately accounted for.

Die Anwendbarkeit der β-Ruckstreumethode zur Korrosionsuntersuchung beruht auf der Beziehung zwischen Ruckstreukoeffizienten und Ordnungszahl sowie Schichtdicke des streuenden Materials, wobei die effektive Ordnungszahl der an der Metalloberflache entstehenden Korrosionsprodukte bei der atmospharischen Korrosion immer kleiner ist als die Ordnungszahl des Metalls (Ausnahme: Be). Fur den Fall der atmospharischen Korrosion von Stahl wurde gute Ubereinstimmung zwischen berechneten und gefundenen Werten der effektiven Ordnungszahl erst nach Erhitzen auf 500°C erhalten, da hierbei Wasser und Carbonat abgegeben werden. Voraussetzung fur die Anwendbarkeit bei Korvosionsuntersuchungen ist ferner moglichst gleichmasiger Angriff und moglichst gleichformige Zusammensetzung der Korrosionsprodukte. Fur die Empfindlichkeit und Genauigkeit der Messung ist es zweckmasig, keine Strahler zu hoher Energie zu benutzen. A study of corrosion with β-reflection The application of the β-reflection method in corrosion research is based on the relation between reflection coefficient and atomic number and coating thickness of the reflecting material, the effective atomic number of the corrosion products formed on the metal surface during atmospheric corrosion being always smaller than the atomic number of the particular metal (exception: Be). As far as atmospheric corrosion of steel is concerned, good agreement has been obtained between calculated and measured values of the effective atomic number only after heating to 500° C, because water and carbonate are removed at that temperature. Another condition governing application to corrosion research is uniformity of attack and uniformity of composition of the corrosion products. As to the sensitivity and accuracy of the measurement it is useful not to employ radiation sources having too high a radiation energy.

1. Of the additives studied, under the test conditions used, the following protect metals most effectively from atmospheric corrosion: additive AKOR-2; additive composition KP-2 (except on cast iron); and the multifunctional additives PMSya and ASK. 2. The greatest reduction in potential corrosiveness of base oil DS-11 is observed when additives PZ-23k, PMSya, or AKOR-2 are added to it. 3. The absence of a direct dependence between the effect of additives on potential corrosiveness of an oil and its ability to protect metals from atmospheric corrosion has been shown.

In einer fruheren Arbeit wurde die Wirksamkeit von punktformigen Ansammlungen von Eisen(II)-sulfat beim atmospharischen Rosten beschrieben. Der elektrochemische Mechanismus dieser Eisen(II)-sulfat-Nester kann nur in groben Zugen angegeben werden, da es bisher nur uberraschend wenige experimentell belegte Arbeiten uber das atmospharische Rosten gibt. Anhand einer schematischen Darstellung eines Nestes werden die Vorgange an der Anode und der Kathode sowie die sich ergebende Bedingung der Elektronenleitfahigkeit der beteiligten Eisenoxyde erortert. Die Initialphase, der Wachstumsvorgang, die Stabilitatsfaktoren und die Beziehungen zu den bisherigen Anschauungen uber das atmospharische Rosten werden diskutiert. Veroffentlichungen uber die Zusammensetzung des Rostes, seine Redoxfunktion sowie uber bestimmte, fur die Theorie der Nester bedeutsame Eisenoxydhydroxyde werden referiert bzw. Angefuhrt. Theoretical interpretation of the ferrous(II) sulphate concentrations in atmospheric rust–part II In an earlier article, the effect of point-shaped concentrations of ferrous(II) sulphate on atmospheric corrosion was described. The electro-chemical mechanism of these ferrous (II) sulphate concentrations can only be indicated in broad outline, since atmospheric corrosion has so far been the subject of surprisingly few publications supported by experimental research. On the basis of a schematic presentation of such a concentration, the phenomena at the anode and cathode and the resulting condition of the electronconductivity of the iron oxides concerned are discussed. The discussion then extends extends to the initial phase, the growth phenomena, the stability factors and the relationship with previous theories on atmospheric corrosion. Reference is made to publications on the composition of the rust, its redox function, and certain iron oxide hydroxides which have an important bearing on the theory of these concentrations.

1. Determinations of the rate of corrosion of lead anodes in the absence of a current made it possible to evaluate the effect of this phenomenon on the composition of the solution employed. 2. By using independent regulation of anodic currents and combining soluble anodes with an insoluble anode, it is possible to ensure that the electrolyte composition remains constant. 3. An effective method has been proposed for protecting electrolytic copper-lead alloy powders against atmospheric corrosion, involving stabilizing treatment in a 1% silicate cement solution.

Eine Reihe von Erscheinungen, die dem Rostschutzfachmann gelaufig sind, wie die kornige Beschaffenheit des an der Atmosphare entstandenen Rostes (Rostpusteln, Rostwarzen), der ungleichmasige Angriff der Eisenoberflache beim atmospharischen Rosten, die pustelformige Unterrostung und die punktformige Durchrostung von Anstrichen waren bisher in den Einzelheiten nicht befriedigend erklart. Eine anschauliche Erklarung gelang aufgrund des experimentellen Nachweises von Eisen(II)-sulfat-Nestern im Rost, anknupfend an Arbeiten von G. Schikorr und J. E. O. Mayne. Die Folgerungen fur die in der Praxis ublichen Entrostungsverfahren werden diskutiert. Die theoretische Deutung der Eisen(II)-sulfat-Nester soll in einer zweiten Veroffentlichung mitgeteilt werden. Investigations into the effect of ferrous (II) sulphate on atmospheric corrosion and sub-surface corrosion of coats of paints. – Part I Up to now, there have been no satisfactory explanations of all the details of certain phenomena well known to the corrosion protection expert, such as as the granular nature of atmospheric rust (rust “pimples” or “warts”), uneven effect of atmospheric corrosion on the iron surface, the pimple-shaped corrosion and pit-shaped corrosion of coats of paints. A satisfactory explanation has been found on the basis of the experimental detection of ferrous (II) sulphate concentrations in the rust, in connection with the research work carried out by G. Schikorr and J.E.O. Mayne. The consequences in respect of the derusting methods normally used in practise are discussed. The theoretical interpretation of the ferrous (II) sulphate concentrations will be the subject of a second publication.

The nature and extent of the relationships between the corrosion of two mild steels of different copper content, and atmospheric pollution were investigated at 22 selected sites in the Sheffield area. This was part of a general investigation into atmospheric corrosion of ferrous metals. The results confirmed that there was an important relationship between the corrosion of steel and the atmospheric pollution by smoke and sulphur dioxide. However, only about 50% of the variations in corrosion rates at different sites could be attributed to sulphur dioxide, measured in this investigation by the Volumetric Method. Smoke intensity had an influence on the corrosive rate of steel similar to that of sulphur dioxide but the correlation between sulphur dioxide and smoke was high, so that their effects on the corrosion rate could not be considered as independent. Their combined effect was only slightly greater than their individual effects.The corrosion rate could not be accurately predicted from a knowledg...

An Hand von Literaturangaben werden einige wesentliche Merkmale der atmospharischen Korrosion untersucht. Es wird zunachst die mogliche Rolle der Wasseradsorption diskutiert und der Einflus von Verunreinigungen der Luft und der Metalloberflache auf das Auftreten angreifender Elektrolyte dargelegt. An Hand der elektrodenkinetischen Grundlagen wird speziell fur Eisen und Stahl, mit Anmerkungen zu Kupfer und Zink, der Mechanismus und der geschwindigkeitsbestimmende Schritt der gleichmasgen Korrosion mit Wasserstoffabscheidung, Sauerstoffreduktion und Schwefeldioxydreduktion diskutiert. Im Zusammenhang mit der Frage der ungleichmasigen Korrosion insbesondere der mit Oxydfilmen behafteten Metalle werden die Bedingungen fur das Zustandekommen der verschiedenen Typen von Beluftungselementen dargelegt. Electro-chemical characteristics of atmospheric corrosion On the strength of published data, some essential characteristics of atmospheric corrosion are investigated, First, the part played by water adsorption is discussed and the influence on the emergence of corrosive electrolytes of impurities in the air and on the metal surface explained. On the basis of the electrode-kinetic conditions, the author then deals – especially for iron and steel, but with some comments on copper and zinc – with the mechanism and stages which govern the corrosion rate of uniform corrosion consisting of hydrogen segregation, oxygen reduction, and sulphur dioxide reduction. In connection with the question of non-uniform corrosion, especially of those metals affected by oxide films, the conditions for the appearance of the different types of differential aeration cells are discussed.

The atmospheric corrosion of NaCl-contaminated Fe has been investigated by a gravimetric method. The atmosphere, which consists mainly of N 2 , had an O 2 pressure which was varied between 0·2 and 25 torr. The humidity was 92·5 per cent. At low O 2 pressure, a time-independent corrosion rat was observed. The rate increases with increasing O 2 pressure and increasing amounts of NaCl on the metal surface. Above 7 torr O 2 pressure, a meta-stable state was first formed, at which the corrosion rate was independent of pressure. After a while, increasing corrosion was observed in this pressure range. The corrosion rate was then proportional to the time, until a limiting rate was reached.

Die Methode beruht auf der Druckanderung im abgeschlossenen Probenraum, gemessen m Vergleich mit einem Vergleichsvolumen. Die mittlere abtragung wird berechnet aus dem Sauerstoffverbauch, mit der Annahme, das das Eisen im Rost dreiwertig vorliegt. In reinem Sauerstoff, gesattigt mit Wasserdampf, ist die Korrosion vernachlassigbar klein; erst Zugabe von Schwefeldioxid fuhrt zu merklicher Abtragung, wobei die Geschwindigkeit etwa linear mit der chwefeldioxidmenge ansteigt. Gleich grose Schwefeldioxidmengen wirken starker, wenn sie einmal, und zwar gleich zu Beginn, als wenn sie mehrmals in zeitlichem abstand und kleineren Mengen zugesetzt werden. Gas-volumetric measurement of atmospheric corrosion The method is based on the variation of pressure in the closed test chamber, measured by comparison with an identical volume. The mean corrosion loss is calculated from the oxygen consumption, assuming that the iron in the reust is in the trivalent state. In puer oxygen saturated with moisture, corrosion is negligible; only addition of sulphur dioxide results in notable corrosion losses, the rate of corrosion increasing about linearly with sulphur dioxide quantity. Equal sulphur dioxide quantities have a more pronounced effect when added in one step immediately at the beginning, than when added successively in smaller portions.

Atmospheric corrosion products of copper were identified by scanning electron microscopy, X-ray microanalyzer, X-ray diffraction, and electron diffraction. The samples were exposed to the air for periods of 1/2, 1, 3, and 6 months. The results obtained were as follows: (1) The corrosion products were composed of chlorides, sulfur compounds, and oxides. Among them, the constituents identified were Cu2O, CuCl, 3Cu(OH)2⋅CuCl2, and Cu2S. (2) In conclusion, it is very defective to make analysis of the corrosion products only by X-ray diffraction and electron diffraction with simple results of measurements. Therefore, the analysis must be made with comprehensive knowledge by using other various techniques as possible.

Die Zusammensetzung der auf nichtmetallischen Materialien (Glas) sowie auf Metallen (Cu, Zn, Fe) an SO2-haltiger Atmosphare entstehenden Elektrolytfilme wurde untersucht, wobei sowohl frische als auch vorkorrodierte Proben verwendet wurden. Dabei stellte sich heraus, das das in der Losung aufgenommene SO2 sehr rasch zu SO oxydiert wird, wenn der Elektrolytfilm geloste Anteile aus den Korrosionsprodukten enthalt. Der pH-Wert des Elektrolyten andert sich bei 1 bis 55 ppm SO2 in der Atmosphare nur wenig und nicht entsprechend dem SO2-Partialdruck. Properties of electrolyte films formed through atmospheric corrosion An investigation has been carried out into the composition of the electrolyte films which are formed on non-metallic materials (glass) as well as on metals (Cu, Zn, Fe) in an atmosphere containing SO2. Fresh as well as pre-corroded specimen were used. It was found that the SO2 absorbed in the solution is very rapidly oxidized into SO if the electrolyte film contains dissolved particles of the corrosion products. With 1 to 55 ppm SO2 in the atmosphere, the change in the pH value of the electrolyte is but small and does not vary with the SO2 partial pressure.