A straightforward, explicit equation was developed previously to estimate an "equivalent" velocity in the rotating cylinder electrode that might best simulate the velocity in a pipe. That equation used friction factor vs Reynolds number relationships valid to Reynolds numbers of similar to10(5). A similarly straightforward, explicit equation has been derived here that extends the estimate to much higher Reynolds numbers. Use of more complicated alternative equations while being more exact have been more difficult to use, requiring iteration to calculate the velocity. The equation reported here enables a reasonable estimate of the cylinder velocity to be calculated directly from the pipe velocity at higher Reynolds numbers without the need for iteration.

Growing environmental concerns regarding the use of heavy metals in coating formulations have led to a new coating strategy using inherently conducting polymers (ICP), such as polyaniline (PANI). as a key component. The principal potential advantage offered by the ICP coating technology is toleration of pinholes and minor scratches. This paper introduces the use of new PANI formulations that are doped with phosphoric acids. Salt fog exposure tests point to phosphoric acid salts of PANI being more effective for corrosion protection than traditionally used sulfonic acid salts. Scanning reference electrode technology (SRET) data support the salt fog results in that the sulfonic acid dopants exhibited an increasing galvanic activity with time while the phosphonic acid dopants, showed a decrease in activity with time, indicating passivation. A qualitative model is proposed which entails passivation of the metal surface through anodization of the metal by PANI and formation of an insoluble iron-dopant salt at the metal surface.

This chapter contains sections titled: Introduction Thermodynamic potential–pH diagrams Cyclic potentiodynamic polarization scans for predicting localized corrosion Polarization resistance technique for corrosion prediction Corrosion prediction using electrochemical impedance spectroscopy Testing for velocity-sensitive corrosion—rotating-cylinder electrode Conclusions List of symbols (by equation) References

Abstract Potential-pH (Pourbaix) diagrams are used as road maps for aiding in predicting the most stable states of a metal, its corrosion products, and its associated ions in an aqueous solution. I...

Corrosion prediction technology has advanced significantly over the past 30 years. Making practical use of these advances for routine, rapid corrosion prediction in industrial environments has been and continues to be a challenge. This paper examines several of the advances over this period from the standpoint of how they can be used to make field predictions. The techniques discussed are theoretical potential-pH diagrams, the rotating cylinder electrode, and artificial neural networks. In addition, the internet now enables web-interfaced "intelligent" corrosion tools to be widely accessible. Use of this information medium could enable the corrosion practitioner to capture the "collective corrosion experience" of many for corrosion prediction. This potential is discussed from the standpoint of several corrosion prediction applications that have been made internet-accessible.

Two artificial neural network-expert system programs originally developed for stand alone computers were modified so as to be internet accessible. These intelligent tools predict the propensity for localized corrosion from cyclic potentiodynamic polarization scans and the chemical compatibility of elastomers and some thermoplastics from a sequential immersion test. Examples discussed show that the functionality of the programs has not been compromised by the modification for the internet. The benefits such internet accessibility can provide are discussed in this paper.

A debate surrounds the question of whether to use equality of the mass-transfer coefficient or of the fluid shear stress at the wall to define flow parameters to simulate velocity-sensitive corrosion between geometries. In principle, this debate may be circumvented if both parameters could be simultaneously similar in the modeled and modeling geometries. To explore this possibility, an equation derived from the analogy among heat, mass, and momentum transfer was used to estimate rotating cylinder electrode diameters and rotation rates that enable simultaneous similarity of the mass-transfer coefficient and the shear stress at the wall between hydraulically smooth cylinders and straight pipes. The results imply that under some but not all conditions, practical cylinder diameters and rotation rates may be found.

Of the Laboratory devices available for examining the effects of single-phase fluid flow on corrosion, the rotating cylinder electrode is probably one of the simplest devices to construct and operate under defined hydrodynamics in the turbulent flow regime. This review examines several areas important to the use of this device for examining velocity-sensitive corrosion in single-phase fluids:-the numerous correlations that have been developed to calculate the Sherwood number (mass-transfer coefficient)from the Reynolds and Schmidt numbers for a hydraulically smooth cylinder surface-the effect that surface roughness caused by corrosion and deposits might have on the correlations-a methodology and its limitations for estimating the conditions in the rotating cylinder electrode that could best indicate if mass transfer influences corrosion in several other geometries-a survey of a variety of corrosion-related studies using the rotating cylinder electrode to provide an overview of the large number of applications of this technology and a source for further readingAlthough this device has been applied successfully, users have sometimes overlooked its limitations, and some of its characteristics still need further attention.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation David C. Silverman; Editorial: A Perspective on Generating and Handling Corrosion Inhibitor Related Data. CORROSION 1 January 2004; 60 (1): 3–4. doi: https://doi.org/10.5006/1.3299231 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest Search

N-acyl glutamates as a class of amido acid compounds were discovered to inhibit the corrosion Of aluminum but accelerate the corrosion of magnesium. Assuming that the carboxylate moiety is the group affecting corrosion, this behavior is consistent with previous results for aluminum that showed corrosion inhibition by straight-chain alpha,omega dicarboxylates. But these findings deviate from previous results for magnesium that showed corrosion inhibition by straight-chain monocarboxylates. This acceleration has been tentatively attributed to the acyl glutamates being able to form stable, soluble complexes with magnesium ions.

Wavelet transform methods were applied to electrochemical noise voltage vs time data to investigate whether these transforms offer an improved methodology for discriminating among electrochemical noise signals arising from different types of localized corrosion. The ultimate goal of this effort is to provide a framework by which electrochemical noise data might offer more reliable, real-time predictions of corrosion. A number of alloy-environment combinations known to cause pitting and crevice corrosion were used. The signals were analyzed by using conventional signal processing techniques in the time and frequency domains and by using wavelet techniques in the time-frequency phase plane. A method was proposed to identify and visualize the corrosion intensity from the phase plane data. The predictions are compared with microscopic visual examination of the corroded specimens. The agreement provides evidence that wavelet transforms can offer an enhanced ability to categorize different types of electrochemical noise responses.

The objective of this paper is to explore the use of wavelet transform methods in the characterization and identification of intensity and type of localized corrosion using electrochemical noise (in this case, fluctuations in potential). A series of experiments were conducted using two identical stainless steel electrodes inserted into known corrosive media. The fluctuations in corrosion potential (electrochemical noise) generated from these electrodes were monitored periodically (about every hour) over a few days. These fluctuations were stored in blocks of 1024 data points (collected at 1 Hz). They were analyzed by using conventional signal processing techniques in the time and frequency domains as well as by using wavelet techniques in the time-frequency phase plane. The results were compared with microscopic visual examination of the corroded surface to correlate the electrochemical noise signal with the type and extent of corrosion. The results show that wavelet transforms hold promise in decoding this noise pattern. A method to compute the corrosion intensity from the phase plane data is proposed and is in qualitative agreement with the experimental results.

Simulation of velocity-sensitive corrosion in the laboratory for predicting similar corrosion in the field is of ongoing interest. Such an approach seems to be especially practical when corrosion is controlled by the rate of mass transport to or from the surface. Such control, when measured under appropriate conditions in the laboratory, should be observed in the field. The present research goal was to review equations that allow the corrosion practitioner to estimate easily velocities in the laboratory that would simulate flow conditions in other geometries.

The cyclic potentiodynamic polarization technique provides a reasonable, rapid method for qualitatively predicting the propensity of an alloy to suffer localized corrosion in the form of pitting and crevice corrosion. Better and more accurate techniques are available for estimating general corrosion rates. This paper outlines the features that have been found useful for interpreting the polarization scan along with an example of how such an interpretation might be made. The paper follows with a discussion of some of the effects that uncompensated solution resistance, inappropriate scan rate, and improper point of scan reversal can have on the polarization scan features and how these effects might influence the interpretation.

Growing environmental concerns regarding the use of heavy metals in coating formulations has led to a new coating strategy employing inherently conducting polymers (ICP) as a key component. ICPs (such as polyaniline, polypyrrole and polythiophene) are electrically conductive owing to a system of conjugated double bonds. Observations of metal passivation complement this conductive nature and offer a viable alternative to traditional corrosion protection (1–8). A key potential advantage that the ICP coating technology offers is toleration of pin holes and minor scratches. The basis for this argument is that, since the ICP coating is conductive, the entire coating acts to passivate any areas of exposed metal. This paper describes a model for polyaniline (PANI) corrosion protection and presents data which clearly demonstrate significant corrosion protection in a salt fog environment. ESCA and electrochemica data are presented which show that an Fe-PANI complex is formed in the process of coating steel with PANI. The Fe-PANI complex is shown to catalytically reduce oxygen. Preliminary electrochemical impedance results are also presented which show an additional time constant at 20 kHz, which appears to correlate with the effectiveness of PANI toward corrosion protection.

Polyaspartic acid, a polymeric form of aspartic acid (C4H7NO4), was examined as a corrosion inhibitor for steel as a function of pH, temperature, and hydrodynamic conditions. The temperature ranged from 25 degrees C to 95 degrees C, and the concentration ranged from < 1 wt% to similar to 10 wt%. Experimental procedures included electrochemical impedance spectroscopy (EIS), the rotating cylinder electrode (RCE), and coupon Immersion. At low to neutral pH values, polyaspartic acid increased the corrosion rate of steel At high pH (< similar to 10), polyaspartic acid was a reasonably robust corrosion inhibitor. Between pH 7 and 10, corrosion in the presence of polyaspartic acid was a complex function of temperature, concentration water quality, and hydrodynamic conditions. By combining corrosion potential measurements with speciation diagrams obtained by titration, a reasonably cohesive explanation of the behavior was developed.