EXPERIMENT
CORROSION OF METALS
Objective
The objective of this experiment is to measure the corrosion rate of two different metals and to show the effectiveness of the use of inhibitors to protect metals from corrosion.
PROCEDURE
CAUTION: BE SURE YOU UNDERSTAND HOW TO OPERATE THE EQUIPMENT BEFORE BEGINNING THE EXPERIMENT
If you are not familiar with the equipment ask for help from your instructor. DO NOT START INDISCRIMINATELY MAKING ADJUSTMENTS TO THE EQUIPMENT.
Your group will be provided with samples of 1018 steel and brass. Prepare the sample (metal exposed side) for metallographic observation (polish/grind using 400 grit, 600 grit sandpaper and 1 micron powder). Check the specimens under the microscope to be sure that they are well polished. Observe the surface of each specimen before and after corrosion takes place. Take photos.
CAUTION: The equipment used to measure corrosion rates is very delicate. Use extreme care when handling.
Pour about 400cc tap water (room temperature) into the beaker that makes up the electrochemical cell and add approximately one teaspoon of salt to form a solution. Then place one prepared (steel or brass) specimen in the cell setup with the calomel standard reference electrode and the counter electrode. Check to be sure that the counter electrode and the sample surface are parallel (not touching).
Connect the leads from the EG&G VersaStat to the electrochemical cell. The Green wire attaches to the working electrode (the sample), the Red wire attaches to the counter electrode, and the White wire attaches to the reference electrode.
If the machine is not already on, boot up the computer and at the DOS C:\> prompt type: corr [ENTER].
When the title screen comes up hit any key to display the Main menu. Pick "SetUp" from the main menu to display the Set up menu. Pick "Get Set Up".
You will then be asked to "Enter setup filename for recall." Type: 227L [ENTER].
The screen will now display the test parameters to be used for your experiment. Your group will have to enter the correct sample area and specimen density in their respective fields on the test Setup Screen.
Once the correct test parameters have been entered for your specimen, your group is ready to run a test. Choose the Run command from the menu and turn the Cell Switch located on the front of the EG&G Versa Stat to the ON position. A plot of your test will appear on the computer screen once the test begins. The test runs for 15 minutes.
When the test stops, turn the Cell Switch to the OFF position. Save your data to a 3.5" floppy before beginning any further tests. Put a 3.5" floppy disk into the A drive. To save your data first save your data on the C drive using the "Save" command in the "File" menu. Next recall your data using the "Get Data" command in the "File" menu. Finally, transfer the data to your diskette in the A drive by choosing the "Export Data" from the "File" menu. Type in a file name for your data including an A drive path. (For example, you can type: a:\steel).
Repeat this procedure for the other metal (steel or brass) sample.
Next put about 400cc of the prepared antifreeze/water mixture (50% ethylene glycol) into the electrochemical cell and repeat the experiment for the remaining samples. Note the corrosion inhibiting effect of the antifreeze. Normally, when antifreeze is added in small concentrations to an environment, the corrosion rate decreases. In a sense, an inhibitor can be considered a retarding catalyst. The effectiveness of an inhibitor can be measured basedon:
Degree of effectiveness of inhibitor = Corrosion rate without inhibitor / Corrosion rate with inhibitor
When a rate is determined using the mpy equation once the rate has plateaued.
Attachment:- Attachments.rar