Data acquisition, corrosion

Can the required data be acquired Can the desired areas of interest (appropriate interface or corrosion area) be identified for analysis Is data acquisition fast enough to generate desired data in reasonable time for allowable cost Can contamination mask the desired signals Is the appropriate type of data being taken ... 

Data Analysis. Data analysis is, of course, directly related to data acquisition. However, not all good data is or can be completely analyzed. For example, McIntyre (J5) has observed that "a broad base in chemical shift data has been slow in developing" for XPS data. Until such a data base existed, it was difficult for both expert and non-expert to interpret spectra from corrosion products, particularly on complex alloys. The Handbook of X-Ray Photoelectron Spectroscopy (27) and collections of Auger parameter data (32 ) are examples of data compilations very useful to a researcher trying to interpret measurements of corrosion products. 

The purpose of this section is to show, by example, how the concerns of technique selection, potential problems, data acquisition and analysis have been applied for several different corrosion problems and techniques. Examples of fundamental research work and industrial problem solving have been included to show the range of applicability of the techniques. In most cases, more than one technique was used to solve the problem. Frequently, a surface analysis technique was used in combination with one or more other types of analysis method. These examples are not comprehensive it is hoped that sufficient references have been supplied to enable the reader to find other work of relevant interest. 

Computers and programs are also important in corrosion monitoring systems, such as an automated constant rate extension system (A Cert) shown schematically in Figure 5.5. This system may be used for conducting corrosion and cracking evaluation tests. The system is capable of initiation and conducting tests as well as data acquisition and analysis. There is very little human intervention and the system is capable of corrosion evaluation in environments which are difficult to simulate. This system is a... 

M.W. Kendig, U. Bertocci and J.E. Strutt (Eds.), Computer Aided Acquisition and Analysis of Corrosion Data, The Electrochemical Society, New York, 1985. 

Electrochemistry is a field, where control of experiments and data acquisition methods do not differ greatly, but proper interpretation of measured data gives information on several different phenomena. In electrochemical experiments one controls the system with electrical quantities and also measures electrical quantities, i.e. voltage and current. The electrochemical corrosion process, its probability and rate can be described as a function of three variables potential, current and time. Other electrical and electrochemical parameters can be derived from these variables. As an electrochemical process, corrosion can also be studied with electrical measurement methods. The measurements are suitable for automation which has the following advantages ... 

B. Savova-Stoynov and Z. Stoynov [1985] Computer Analysis of Non-Stationary Impedance Data, Proc. Symp., Computer Aided Acquisition and Analysis of Corrosion Data, ed. M. W. Kendig, U. Bertocci, and J. E. Strutt, Electrochem. Soc. Inc., Pennington, Vol. 85-3, 152-158. 

The measurement system consists of a calculator with a memory that controls data acquisition, data averaging, data storage, and data transmission to a large scale computer. These multifrequency impedence measurements are rapid and provide a rather complete description of the corrosion behavior in a very short time. 

The electrochemical studies namely cyclic voltammetry and Tafel curves carried out to test the protective layer were conducted using the PGZ 402 Dynamic EIS Voltalab. For the data acquisition the Voltamaster 4, version 7.08, was used. This specialized software can determine, based on references, from the Tafel test s values, the exact corrosion speed, measured in mm/ year. 

Corrosion tests are the best appropriate technique for acquisition of data for material selection. In most corrosion data survey handbooks, corrosion rates are evaluated for just a few factors (e.g. temperature and concentration). However, there are many other factors that influence corrosion rates. While they are often extremely important, it is impossible to list them all in a review of this type. 

The most recent results of applying in situ STM/AFM to studies of corrosion convincingly demonstrate that novel and interesting images of solid-interface processes can be obtained. In fact, the images may be collected and presented consecutively, thereby enabling the viewer to follow the corrosion process as a moving picture in real time. In combination with simultaneous acquisition of electrochemical data, such as current-potential curves, these techniques provide excellent tools for... 

The available data from the services indicate that corrosion in weapons systems is the primary cost driver in life-cycle costs (46). Quantifying corrosion is difficult as neither the mechanisms nor the methodologies exist to quantify accurately. Analysis of field data reveals instances where questionable materials selection early in the acquisition process has led to enormous unanticipated increases in life-cycle costs because of corrosion (J Argento, US Army TACOM-ARDEC, Picatinny Arsenal, NJ, Personal Communication, 1999). In view of force reduction and a reduction in budgets, consideration must be given to the selection of advanced materials, processes, and designs that will require less manpower for corrosion inspection and maintenance. 

Corrosion tests are primarily aimed at the acquisition of data in a relatively short time compared to service lifetime, to predict service behavior. Corrosion test methods may be divided into three categories ... 

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