DK171925B1 - Method for determining the rate of corrosion in reinforced concrete - Google Patents
Method for determining the rate of corrosion in reinforced concrete Download PDFInfo
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Description
DK 171925 B1DK 171925 B1
Opfindelsen angår en fremgangsmåde til bestemmelse af korrosionshastigheden i f.eks. armeret beton.The invention relates to a method for determining the rate of corrosion in e.g. reinforced concrete.
Fra engelsk patentansøgning nr. 2.200.459 er det kendt at anvende en korrosionsdetekterende sonde omfattende en guard-5 ring til styring af retningerne af de elektriske strømme til armeringen. Ud fra korrosionsstrømmen er det ved hjælp af denne sonde muligt at måle korrosionshastigheden. Målingen tager imidlertid forholdsvis lang tid.From English Patent Application No. 2,200,459, it is known to use a corrosion detecting probe comprising a guard ring for controlling the directions of the electrical currents for the reinforcement. From this corrosion stream it is possible to measure the corrosion rate by means of this probe. However, the measurement takes a relatively long time.
Fra US patentskrift nr. 5.259.944 kendes en korrosionsmåler 10 til bestemmelse af korrosionshastigheden ved en måling af polarisationsmodstanden. Der tilføres målestrøm fra et mod-elektrodesystem.US Patent No. 5,259,944 discloses a corrosion meter 10 for determining the rate of corrosion by measuring the polarization resistance. Measuring current is supplied from a counter-electrode system.
Endvidere er det kendt at foretage korrosionsmålinger ved en galvanostatisk pulsmetode. Måletiden i det enkelte målepunkt 15 vil derved kunne reduceres. Dette er imidlertid ikke tilstrækkeligt til at kunne måle korrosionshastigheden.Furthermore, it is known to make corrosion measurements by a galvanostatic pulse method. The measurement time in the individual measuring point 15 will thereby be reduced. However, this is not sufficient to measure the corrosion rate.
Formålet med opfindelsen er at anvise, hvorledes en måling af korrosionshastigheden vil kunne foretages hurtigere og mere nøjagtigt end hidtil kendt.The object of the invention is to show how a measurement of the corrosion rate can be made faster and more accurately than hitherto known.
20 Dette formål er ifølge opfindelsen opnået ved, at der i forbindelse med en referenceelektrode og en strømtæthedsstyret modelektrode anvendes en galvanostatisk pulsmetode.This object is achieved according to the invention in that a galvanostatic pulse method is used in conjunction with a reference electrode and a current density controlled model electrode.
Opfindelsen skal nærmere forklares i det følgende under henvisning til tegningen, som viser det elektrokemiske kredsløb 25 med et elektrodearrangement til ved hjælp af fremgangsmåden ifølge opfindelsen at bestemme korrosionshastighed af arme-ring i beton.The invention will be explained in more detail below with reference to the drawing, which shows the electrochemical circuit 25 with an electrode arrangement for determining the corrosion rate of reinforcement in concrete by the method according to the invention.
En stålarmering indstøbt i beton vil normalt ikke korrodere som følge af, at der dannes en beskyttende jernoxidfilm, der 30 passiverer stålet under alkaliske forhold. Passiveringen kan 2 DK 171925 B1 imidlertid ødelægges ved, at chlorider trænger ind i betonen, og som følge af karbonatisering, hvorved der starter en korrosion. Under korrosion af stål sker der en elektrokemisk proces, der bevirker, at der dannes korroderende og passive 5 steder på metaloverfladen. Ved anoden er reaktionerneA steel reinforcement embedded in concrete will not normally corrode due to the formation of a protective iron oxide film which passivates the steel under alkaline conditions. However, the passivation can be destroyed by chlorides penetrating the concrete and as a result of carbonation, thereby initiating a corrosion. During steel corrosion, an electrochemical process occurs which causes corrosive and passive 5 sites to form on the metal surface. At the anode are the reactions
Fe=Fe+++ 2e~ (metalopløsning, aktiv korrosion) 3 Fe + H20= Fe304+8H++8e' (dannelse af passivt lag) .Fe = Fe +++ 2e ~ (metal solution, active corrosion) 3 Fe + H2O = Fe304 + 8H ++ 8e '(passive layer formation).
De frigivne elektroner ledes gennem stålet til en lokal katode, hvor de deltager i oxygenreduktionsreaktionen 10 02+2H20+4e*=40H"The released electrons are passed through the steel to a local cathode where they participate in the oxygen reduction reaction 10 02 + 2H20 + 4e * = 40H "
Disse reaktioner fører til dannelse af områder med forskellige elektrokemiske potentialer og resulterer i elektriske korrosionsstrømme i armeringen. Ved at måle potentialerne og korrosionsstrømmene er det i princippet muligt at bestemme 15 korrosionsområderne og vurdere korrosionshastighederne. Hvis omgivelserne ikke ændres, vil fremtidige korrosionsfejl desuden kunne vurderes. I praksis har beton altid revner, flager og tilslagspartikler, der ikke er i ensartet kontakt med armeringen, og som påvirker diffusionskarakteristikkerne. Må-20 linger af elektriske karakteristikker kan derfor kun give en indikation af korrosionstilstanden.These reactions lead to the formation of areas with different electrochemical potentials and result in electrical corrosion currents in the reinforcement. By measuring the potentials and corrosion currents, it is in principle possible to determine the 15 corrosion areas and assess the corrosion rates. Furthermore, if the surroundings are not changed, future corrosion defects can be assessed. In practice, concrete always has cracks, flakes and aggregate particles that are not in uniform contact with the reinforcement and that affect the diffusion characteristics. Measurements of electrical characteristics can therefore only give an indication of the corrosion state.
På den anden side er disse målinger baseret på ikke-destruk-tive metoder, hvilket gør det muligt at opnå information om de processer, der forløber under betonoverfladen. Korrosions-25 graden af indstøbte stålarmeringer er imidlertid til stadighed genstand for bekymring.On the other hand, these measurements are based on nondestructive methods, which enable information to be obtained on the processes that are under the concrete surface. However, the corrosion-25 degree of embedded steel reinforcements is still a concern.
To målemetoder vil blive beskrevet med hensyn til fordele og ulemper, idet en kortlægning af halvcellepotentialet vil blive sammenlignet med måleresultater opnået ved den gal-30 vanostatiske pulsmetode.Two measurement methods will be described in terms of advantages and disadvantages, a mapping of the half-cell potential will be compared with measurement results obtained by the galvanostatic pulse method.
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Kortlægning af halvcellenotentialet (EKP-målina).Mapping of the half-cell potential (ECP target).
Denne målemetode er siden 50'erne blevet anvendt til vurdering af betonbroer. Ved denne metode måles det elektrokemiske potentiale af en armering i forhold til en referenceelektrode 5 på betonoverfladen. For at sikre en god kontakt med referenceelektroden er betonoverfladen forinden blevet vædet. Flere typer referenceelektroder kan komme på tale, eksempelvis kob-ber/kobbersulfat (CSE), sølv/sølvchlorid eller kalomel elektroder (SCE). Potentialerne måles ved hjælp af et højimpedan-10 set voltmeter, og resultaterne vurderes ved hjælp af en computer og tolkes ved hjælp af ASTM 876-87, der er en amerikansk standard.This method of measurement has been used since the 1950s for the assessment of concrete bridges. In this method, the electrochemical potential of a reinforcement is measured relative to a reference electrode 5 on the concrete surface. To ensure good contact with the reference electrode, the concrete surface has been wetted beforehand. Several types of reference electrodes may be discussed, for example copper / copper sulfate (CSE), silver / silver chloride or calomel electrodes (SCE). The potentials are measured using a high-impedance-10 voltmeter, and the results are evaluated using a computer and interpreted using ASTM 876-87, a US standard.
Det er vanskeligt at tolke måleresultater mellem -200 og -300mV vs. CSE. Endvidere er en vurdering af absolutte poten-15 tialer vanskelig. En vurdering af potentialgradienter er en mere hensigtsmæssig procedure. Måleresultaterne præsenteres i form af et ækvipotentialkort, hvor mistænkelige korrosions-områder vil kunne identificeres. De elektrokemiske potentialer påvirkes imidlertid af flere faktorer, såsom kvaliteten 20 af betondæklaget, især dets fugtindhold samt karbonatisering og kloridindtrængning. Også oxygentilgangen påvirker potentialet af det passive stål. Et lavt oxygenindhold resulterer i et fald i potentialet. I våd beton kan der som følge af lav oxygentilgang opstå tilstande, der resulterer i at potentia-25 let falder til særlig lave værdier. Passivt stål kan følgelig også udvise lave potentialer svarende til potentialet for korroderende stål. Passive områder under lave luftningsforhold vil derfor fejlagtigt kunne blive klassificeret som korroderende områder. En yderligere ulempe ved denne metode er, 30 at resultaterne kun giver en indikation af, om korrosion er termodynamisk mulig, og ikke en indikation af korrosionshastigheden.It is difficult to interpret measurement results between -200 and -300mV vs. CSE. Furthermore, an assessment of absolute potentials is difficult. An assessment of potential gradients is a more appropriate procedure. The measurement results are presented in the form of an equipotential map where suspicious areas of corrosion can be identified. However, the electrochemical potentials are influenced by several factors, such as the quality of the concrete coating, especially its moisture content as well as carbonation and chloride penetration. The oxygen supply also affects the potential of the passive steel. A low oxygen content results in a decrease in the potential. In wet concrete, conditions can occur as a result of low oxygen supply, resulting in the potential to drop to particularly low values. Consequently, passive steel may also exhibit low potentials corresponding to the potential for corrosive steel. Therefore, passive areas under low aeration conditions could be mistakenly classified as corrosive areas. A further disadvantage of this method is that the results provide only an indication of whether corrosion is thermodynamically possible and not an indication of the rate of corrosion.
Disse ulemper kan afhjælpes ved hjælp af den galvanostatiske pulsmetode. Denne metode er baseret på en hurtig ikke-de- DK 171925 B1 4 struktiv polarisationsteknik. En kortvarig anodisk strømpuls tilføres galvanostatisk fra en modelektrode anbragt på betonoverfladen sammen med en referenceelektrode af samme type som beskrevet i forbindelse med potentialkortlægning. Den anodi-5 ske strømimpuls resulterer i en ændring i armeringens elektrokemiske potentiale, der registreres ved hjælp af en datalogger. Armeringen polariseres anodisk i forhold til sit frie korrosionspotentiale.These disadvantages can be remedied by the galvanostatic pulse method. This method is based on a fast non-de-structural polarization technique. A short-lived anodic current pulse is applied galvanostatically from a model electrode placed on the concrete surface together with a reference electrode of the same type as described in connection with potential mapping. The anodic current pulse results in a change in the electrochemical potential of the reinforcement recorded by a computer logger. The reinforcement is anodically polarized to its free corrosion potential.
Polariseringsgraden af armeringen afhænger imidlertid af kor-10 rosionstilstanden. Armeringen er let at polarisere i den passive tilstand, svarende til at der er en stor forskel mellem det frie korrosionspotentiale og det polariserede potentiale. Denne forskel er væsentligt mindre for en korroderende armering. Den galvanostatiske pulsmetode kan derved give en mere 15 detaljeret information om korrosionenstilstanden.However, the degree of polarization of the reinforcement depends on the corrosion state. The reinforcement is easy to polarize in the passive state, as there is a large difference between the free corrosion potential and the polarized potential. This difference is significantly smaller for a corrosive reinforcement. The galvanostatic pulse method can thereby provide more detailed information on the corrosion state.
Udover den mere detaljerede kvalitative information om klassifikation af passive og korroderende områder giver denne metode også mulighed for kvantitativ vurdering, idet den muliggør en beregning af korrosionsstrømmen. Hvis arealet af 20 den polariserede armering er kendt, kan man ud fra korrosionsstrømmen beregne korrosionshastigheden.In addition to the more detailed qualitative information on the classification of passive and corrosive areas, this method also allows for quantitative assessment, enabling a calculation of the corrosion flow. If the area of the polarized reinforcement is known, the corrosion rate can be calculated from the corrosion current.
Potentialerne registreret på overfladen indbefatter et ohmsk spændingsfald, der selvsagt må elimineres.The potentials recorded on the surface include an ohmic voltage drop, which of course must be eliminated.
Ved tilførsel af en konstant strøm Iapp til armeringen kan det 25 polariserede potentiale Vt af armeringen udtrykkes ved vt=IapptRpf1-exP(-tRpcdi) 1 + Rn3 hvorBy applying a constant current Iapp to the reinforcement, the polarized potential Vt of the reinforcement can be expressed at vt = IapptRpf1-exP (-tRpcdi) 1 + Rn3 where
Rp = polarisationsmodstandenRp = polarization resistance
Cdl = dobbeltlagskapaciteten 30 Rq = den ohmske modstand i betonen.Cdl = double layer capacity 30 Rq = the ohmic resistance in the concrete.
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For at vurdere værdierne af Rp og Cdl i forhold til den ohmske modstand Rn, kan ligningen omskrives tilTo evaluate the values of Rp and Cdl with respect to the ohmic resistance Rn, the equation can be rewritten to
In “In (IjrøpRp) -t/Rj,Cal hvor Vmax er steady state potentialet. Ved en logaritmisk af-5 bildning af Vt som funktion af tiden t fremkommer der en ret linie.In “In (IjrøpRp) -t / Rj, Cal where Vmax is the steady state potential. By a logarithmic representation of Vt as a function of time t, a straight line appears.
Ved en extrapolation af denne rette linie til t=0 under anvendelse af mindste kvadraters metode opnås en afskæring svarende til ln(IappRp) og en hældning på l/RpCdl. Det resterende 10 overpotentiale svarer da til det ohmske spændingsfald IappRQ. Efter bestemmelse af polarisationsmodstanden Rp ved denne metode kan korrosionsstrømmen Icorr beregnes ud fra Stern-Gearys ligning.By extrapolating this straight line to t = 0 using the least squares method, a cut equal to ln (IappRp) and a slope of l / RpCdl are obtained. The remaining 10 overpotentials then correspond to the ohmic voltage drop IappRQ. After determining the polarization resistance Rp by this method, the corrosion current Icorr can be calculated from Stern-Geary's equation.
Ico rr^/Bp 15 hvor B er en empirisk værdi, der for aktivt korroderende stål er 25 mV og for passivt stål er 50 mV.Ico rr ^ / Bp 15 where B is an empirical value that for active corrosive steel is 25 mV and for passive steel is 50 mV.
Der er udført målinger på konstruktioner i våde og anaerobe omgivelser. I sådanne omgivelser kunne halvcellepotential målinger (EKP) føre til forkerte tolkninger af korrosionstil-20 standen.Measurements have been made on structures in wet and anaerobic environments. In such environments, half-cell potential measurements (ECPs) could lead to incorrect interpretations of the corrosion state.
Ved galvanostatiske pulsmålinger blev en konstant anodisk strømimpuls på 80-100 μΑ tilført til armeringen fra en modelektrode af rustfrit stål. Strømkilden var forbundet til dataloggeren, og styret af denne.For galvanostatic pulse measurements, a constant anodic current pulse of 80-100 μΑ was applied to the reinforcement from a stainless steel model electrode. The power source was connected to the data logger and controlled by this one.
25 Potentialmålinger blev udført ved hjælp af en sølv/sølv-klo-rid referenceelektrode og registreret i dataloggeren sammen med potentialændringerne som følge af impulstilførslerne.25 Potential measurements were performed using a silver / silver-chloride reference electrode and recorded in the data logger together with the potential changes due to the pulse inputs.
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Potentialændringerne blev registreret med mellemrum på minimum 27 msek og opsamlet i dataloggeren.The potential changes were recorded at intervals of at least 27 msec and collected in the data logger.
Der blev foretaget målinger på en 24 år gammel bærende bjælke. Polarisationstransienten, som er forskellen mellem halv-5 cellepotentialet (det fri korrosionspotentiale) og stabiliseringspotentialet Vmax fra den galvanostatiske pulsmetode, blev registreret flere forskellige steder og afbildet som funktion af positionen i bjælkens længderetning. Varierende polarisa-tionstransienter blev registreret hen langs bjælken, og det 10 viste sig, at der var store forskelle ved enderne og mindre forskelle i midtersektionen. Dette svarer til, at korrosionen er stærkere i midten end ved enderne.Measurements were made on a 24 year old load bearing beam. The polarization transient, which is the difference between the half-cell potential (the free corrosion potential) and the stabilization potential Vmax from the galvanostatic pulse method, was recorded at several different locations and plotted as a function of the longitudinal position of the beam. Varying polarization transients were detected along the beam, and it was found that there were large differences at the ends and minor differences in the middle section. This corresponds to the corrosion being stronger in the middle than at the ends.
En visuel inspektion bekræftede måleresultaterne. Efter fjernelse af betonen blev det nemlig påvist, at korrosionen af 15 armeringen i midtersektionen var stærkere end ved enderne. Ud fra halvcellepotentialmålingerne var det imidlertid ikke muligt at konstatere disse korrosionsforskelle.A visual inspection confirmed the measurement results. After removal of the concrete, it was shown that the corrosion of the reinforcement in the middle section was stronger than at the ends. However, from the half-cell potential measurements, it was not possible to detect these differences in corrosion.
For at opnå en bedre kvantificering af korrosionsaktiviteten blev den effektive polarisationsmodstand bestemt ud fra 20 pulsmålingerne, under antagelse af, at det er det samme areal, som polariseres.To obtain a better quantification of the corrosion activity, the effective polarization resistance was determined from the 20 pulse measurements, assuming it is the same area that is polarized.
Det er imidlertid ikke muligt at beregne korrosionshastigheden ud fra polarisationsmodstanden alene, eftersom det polariserede armeringsareal ikke er veldefineret. Endvidere kan 25 varierende betons resistivitet og armeringsdensitet påvirke resultaterne. For at opnå en sand polarisationsmodstand, som kan omsættes til korrosionshastighed, er det derfor nødvendigt at sikre en ensartet fordeling af polarisationsstrømmene indenfor det afgrænsede armeringsområde.However, it is not possible to calculate the corrosion rate from the polarization resistance alone, since the polarized reinforcement area is not well defined. Furthermore, resistivity and reinforcement density of 25 varying concrete can affect the results. Therefore, in order to obtain a true polarization resistance that can be converted to corrosion rate, it is necessary to ensure a uniform distribution of the polarization currents within the bounded reinforcement area.
30 Fig. 1 viser et blokdiagram med elektrodearrangementet til bestemmelse af korrosionshastigheden ved den galvanostatiske pulsmetode. 1 er en måleelektrode af sølv/sølvchlorid. Via en DK 171925 B1 7 buffer 11 i form af en operationsforstærker er denne måleelektrode 1 forbundet til det øvrige målekredsløb. Omkring måleelektroden l er der en rundtgående modelektrode 2, og omkring modelektroden 2 er der nogle yderligere rundtgående 5 elektroder. Man ønsker nu at kunne styre strømmen fra modelektroden 2 ned mod armeringen 12 i betonen.FIG. 1 shows a block diagram of the electrode arrangement for determining the corrosion rate by the galvanostatic pulse method. 1 is a silver / silver chloride measuring electrode. Via a DK 171925 B1 7 buffer 11 in the form of an operational amplifier, this measuring electrode 1 is connected to the other measuring circuit. Around the measuring electrode 1 there is a circumferential counter electrode 2, and around the counter electrode 2 there are some additional circumferential 5 electrodes. It is now desirable to be able to direct the current from the counter electrode 2 down to the reinforcement 12 in the concrete.
Den valgte strøm udsendes fra modelektroden 2, og spændingen ved modelektroden 2 måles ved hjælp af et dertil sluttet kredsløb 7. Ved hjælp af dette kredsløb 7 påtrykkes en om-10 kringliggende og dertil sluttet tilbagekoblingselektrode 3 det samme potentiale, som måles ved elektroden 2. Derefter måles strømmen i tilbagekoblingselektroden 3, og en spænding proportional med denne strøm tilføres til den ene indgang af en til kredsløbet 7 sluttet differensforstærker 9.The selected current is emitted from the counter electrode 2 and the voltage at the counter electrode 2 is measured by means of a connected circuit 7. By means of this circuit 7, a surrounding and connected feedback electrode 3 is applied to the same potential as measured at the electrode 2. Then, the current in the feedback electrode 3 is measured and a voltage proportional to this current is applied to one input of a differential amplifier 9 connected to the circuit 7.
15 Udgangssignalet af differensforstærkeren 9 styrer en dertil sluttet strømgenerator 10, der sender en strøm ned gennem en dertil sluttet korrigerende elektrode (guardring) 5. Spændingen ved elektroden 5 måles ved hjælp af et dertil sluttet kredsløb 8. Ved hjælp af dette kredsløb 8 påtrykkes en dertil 20 sluttet ringformet tilbagekoblingselektrode 4, der er placeret indvendigt i forhold til elektroden 5, samme potentiale som elektroden 5. Strømmen i tilbagekoblingselektroden 4 måles og skaleres med forholdet mellem arealerne af elektroderne 3 og 4, hvorefter en dertil svarende skaleret spænding 25 fra kredsløbet 8 tilføres til den anden indgang af differensforstærkeren 9.The output of the differential amplifier 9 controls a connected current generator 10 which sends a current down through a connected rectifying electrode (guard ring) 5. The voltage at the electrode 5 is measured by a connected circuit 8. A circuit 8 is applied to this circuit 8. connected thereto annular feedback electrode 4 located internally of the electrode 5, the same potential as the electrode 5. The current in the feedback electrode 4 is measured and scaled with the ratio of the areas of the electrodes 3 and 4, whereupon a corresponding scaled voltage 25 from the circuit 8 is applied to the second input of the differential amplifier 9.
Denne konstruktion vil automatisk indstille sig, således at der er samme strømtæthed ved elektroderne 3 og 4, uanset hvor stor en strøm der leveres af den korrigerende elektrode 5.This construction will automatically adjust so that there is the same current density at electrodes 3 and 4, regardless of how much current is provided by the corrective electrode 5.
30 Modelektroden 2 har fortrinsvis et areal på 16 cm2, tilbagekoblingselektroden 3 et areal på 3 cm2, tilbagekoblingselektroden 4 et areal på 3,7 cm2 og den korrigerende elektrode 5 et areal på 38 cm2.The electrode 2 preferably has an area of 16 cm 2, the feedback electrode 3 has an area of 3 cm 2, the feedback electrode 4 has an area of 3.7 cm 2 and the corrective electrode 5 has an area of 38 cm 2.
8 DK 171925 B18 DK 171925 B1
Et antal elektroniske kontakter sikrer, at der ikke løber strøm i elektroderne, når der ikke skal måles.A number of electronic contacts ensure that the electrodes do not run when not measuring.
Tilbagekoblingselektroderne kan bestå af korroderende metal. Endvidere kan modelektroden og dertil hørende tilbagekob-5 lingselektroder eventuelt være opdelt i segmenter.The feedback electrodes may consist of corrosive metal. Furthermore, the model electrode and associated feedback electrodes may be optionally divided into segments.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DK98195A DK171925B1 (en) | 1995-09-07 | 1995-09-07 | Method for determining the rate of corrosion in reinforced concrete |
| PCT/DK1996/000374 WO1997009603A1 (en) | 1995-09-07 | 1996-09-06 | A method of determining the rate of corrosion in reinforced concrete |
| AU67860/96A AU6786096A (en) | 1995-09-07 | 1996-09-06 | A method of determining the rate of corrosion in reinforced concrete |
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| Application Number | Priority Date | Filing Date | Title |
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| DK98195A DK171925B1 (en) | 1995-09-07 | 1995-09-07 | Method for determining the rate of corrosion in reinforced concrete |
| DK98195 | 1995-09-07 |
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| DK171925B1 true DK171925B1 (en) | 1997-08-11 |
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| JP6540718B2 (en) * | 2016-04-12 | 2019-07-10 | Ｊｆｅスチール株式会社 | Method of evaluating corrosion environment of metallic iron in iron-containing oxide and method of manufacturing granular material |
| DE102016222538B3 (en) * | 2016-11-16 | 2018-02-22 | Fachhochschule Erfurt | Method and arrangement for assessing the corrosion and passivation of the reinforcement taking into account the moisture in reinforced concrete |
| JP2020153782A (en) * | 2019-03-19 | 2020-09-24 | 一般財団法人電力中央研究所 | Corrosion detection device, corrosion detection method, and corrosion detection program |
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| JPS63163266A (en) * | 1986-12-26 | 1988-07-06 | Nippon Steel Corp | Corrosion detecting end of steel products in concrete and method for evaluating corrosion of steel products using said end |
| FR2634888A1 (en) * | 1988-07-26 | 1990-02-02 | Advanced Technologies Internal | METHOD AND DEVICE FOR DETERMINING THE CORROSION SPEED OF A BURIED OR IMMERED CONTINUOUS METAL STRUCTURE |
| US5259944A (en) * | 1990-05-18 | 1993-11-09 | Geotecnia Y Cimientos, S.A.-Geocisa | Corrosion detecting probes for use with a corrosion-rate meter for electrochemically determining the corrosion rate of reinforced concrete structures |
| DE59209299D1 (en) * | 1992-01-16 | 1998-05-28 | Renco S P A | Process for monitoring the state of corrosion of metallic piles and masts embedded in cement foundations |
-
1995
- 1995-09-07 DK DK98195A patent/DK171925B1/en not_active IP Right Cessation
-
1996
- 1996-09-06 WO PCT/DK1996/000374 patent/WO1997009603A1/en active Application Filing
- 1996-09-06 AU AU67860/96A patent/AU6786096A/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| WO1997009603A1 (en) | 1997-03-13 |
| DK98195A (en) | 1997-03-08 |
| AU6786096A (en) | 1997-03-27 |
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