There is available a demo version of this software.
If the "technical" font
is not installed in your computer you need to download it as well.In this work, a multimedia application focused to achieve virtual corrosion
tests on metallic materials is presented as an alternative to in-situ practices.
One of the main targets of this project is centred upon the acquisition
by the students of the knowledge of different types of corrosion processes
that take place in diverse metallic alloys. On the other hand, the project
is aimed at obtaining from the students a familiarisation with the basic
methodology applied to characterise those alloys and their behaviour against
corrosion.
Therefore, the practice is divided into two parts: one to take place in the lab and the other one in the computer room. The experimental part is based on making full immersion testing in order to study the behaviour of different metallic alloys against corrosion. The alloys and the corrosive mediums have been chosen so that a great number of behaviours against corrosion can be detected by simple full immersion testing. It is out of this practice the study of other corrosion processes that need of more complicated experimental devices.
The immersion tests are carried out in two sessions being each one of about two hours. The duration of the tests (about one week) is made conditional on the teaching organisation of the career where it is imparted. Checking the concentration of the used corrosive mediums, the duration of the tests may be changed. On the other hand, the knowledge and skills acquired by the students on other subjects determine the amount of metal/medium to study.
Fig. 1 includes a diagram of the experimental procedure followed by the students in the fulfilment of the tests. The proposed tests have two initial objectives. One of them is to determine the corrosion rate of the systems by measuring weight loss. In addition, the other objective is that the students analyse the changes happened at macroscopic level in the metals and mediums. To achieve that, in the first session, the preparation of the specimens and corrosive mediums is carried out. The samples are provided to the student with round shape, 17 mm of diameter and 2mm of thickness. The students make the superficial preparation of the specimens with wet sandpaper of emery SIC. Afterwards, the samples are washed with distilled water, the grease is removed with acetone and finally they are dried.
Previously to the testing, the samples must be weighed in an analytical scale and its measures are noted using a diameter. These data will be used for determining the corrosion rate. Once samples are weighed, they are subjected to full immersion testing in each of the mediums chosen.
The tests can be carried out in a beaker, taking care of all the sides of the samples to be immersed and exposed to the medium. After one week, the second session takes place in the lab. Then, the changes observed in the system are noted: colour, pH, potential. Besides, changes observed in the metallic specimens are analysed: measures, colour, shape modifications, presence of corrosion products...
In order to find out the weight loss of specimens, it is previously necessary to eliminate corrosion products attached to its surface. To get that, the samples are washed with specific solutions depending on the alloy.
Obtaining the lost weight data, students may calculate the corrosion rate, expressed as time units (miles per year).
Once the tests are finished, for getting deeper into the study of corrosion processes, it would be necessary to use different types of characterisation techniques for metallic alloys. When one has to work with big groups, the use of basic devices like metalographic microscopes is reduced because of the lack of tools, of teachers, or even because of lack of time from the students. Under these circumstances computer tools emerge, like the one presented here.
The goal of the program “Corrosion Virtual Lab” is to provide the student with information about the corrosion of the metallic specimens using different kinds of instrumental techniques.
The program is a multimedia application created from digitised micrographies. The optic microscopic images were taken with a binocular magnifying glass Nikon SMZ and with a metalographic microscope Nikon, Optiphot model. Connecting both tools to a Sony videocamera CCD IRIS makes digitalisation. The signal of the camera is digitised using a FAST FPS60 card connected to a PC. Images have been treated with the program Adobe Photoshop 4.0. The multimedia application has been developed under the supervision of the Computer Science and New Technologies of Education Service (SICYNTE) of the University of Cádiz, using the tutor system macromedia Authorware 4.0. The animated applications have been made with the program Promotion Cosmigo 4.0. The Energy Disperse Spectres included have been taken with a JEOL 8205M microscope provided with a Link analyser AN10000.
Fig. 2 shows the main menu of LVC. The current version incorporates six options. Using the techniques explained before, the information is given as interaction files. The students should be able to analyse the changes suffered by the specimens after their interaction in the corrosive mediums with the supplied information. An objective of the program is not to make the interpretation of the results conditional on the way the program works.
Option 1 lets the student get into the information about the behaviour of an alloy in a corrosive medium. The system to be studied can be chosen with the menus included in the tool bar. Variables of each system are: alloy (brass, copper, steel, stainless steel or aluminium), corrosive medium (nitric acid, sulphuric acid, hydrochloric acid or sodium hydroxide), concentration (0.5M or 1M) and aeration conditions (with or without oxygen). Fig. 3 presents the typical interactive file of Option 1. As you can appreciate, on screen are included low-magnification images before the testing and after the testing with and without corrosion products. In addition, transversal section images before and after the testing are included.
In these files there are some interactions included in the tool bar at the lower side of the screen. It allows you to obtain images with different magnification, its corresponding EDS spectres and the uniform corrosion rate. Database incorporates interactive files corresponding to each of the more than fifty studied systems.
In Option 2, Fig. 4, files are organised so that it is possible to compare in the same screen the behaviour of the five alloys in the same corrosive medium. In this case, a new variable is incorporated, the way of watching alloys you want to compare.
Option 3, Fig. 5, provides the study of the influence of the corrosive medium nature about the behaviour of a determined alloy. That way, in files like the one shown in Fig. 3(c), micrographies corresponding to the same alloy tested in different corrosive mediums are displayed.
The fourth Option makes a description of the experimental procedure followed in the total immersion testing. Originally, this section is included for achieving a revision of the parts making up the experimental procedure followed by the students in the lab. Nevertheless, in cases where the experimental procedure may not be carried out, interactive files included in this section, Fig. 6, make a detailed description of each of all the sections in the proposed testing.
In Option 5, Fig. 7, some animated applications have been included in which mechanisms of different types of corrosion studied models are displayed. For instance, selective dealloying, pitting or uniform corrosion. These animated applications have been made so that the students can interpret experimental data included in the LVC. For this reason, this option is recommended, once the last options have been used, student has analysed data and has elaborated his/her own hypothesis about the behaviour of each system.
One of the main goals of the LVC is that students must be capable of extracting their own conclusions, once virtual practices have been made. In order to prove the ripeness of acquired knowledge, this multimedia application offers the possibility, after finishing all the sections, of doing a test with rejecting answers, Fig. 8. The level of knowledge acquired can be easily measured from questions answered with a grade system incorporated in the application. If minimum required level is not reached, the system itself will recommend the student to make a revision of not understood sections.
