Flight Mechanic

Aircraft Mechanic School Study Supplement for Future Aviation Maintenance Technicians




You are here: Home / Basic Aviation Maintenance / Aircraft Materials Processes and Hardware / Electrochemical Test
Regretfully, Flight-Mechanic will be turning out the lights after fifteen years. Google, in its infinite wisdom, has chosen to remove Flight-Mechanic from its search results (the claim is that the content on this site is spam). We appealed their decision to shut us down, to no avail.

Unfortunately, since Google has a monopoly over internet search, this means that traffic levels on the site will drop to a level that makes maintaining it uneconomic. As time progresses, we will no longer be able to maintain the server space and will remove the site from the internet. Thanks to all who have supported us over the years.

To fight back against the monopolistic practices of companies like Google, we recommend using a competing search engine such as Brave (you get the added benefit of not being spied on by Big Tech) and advocating for anti-trust legislation from your representatives.

Electrochemical Test

Filed Under: Aircraft Materials Processes and Hardware

Prepare a wiring assembly as shown in Figure 5-2, and prepare the two reagents (ammonium fluoride and dimethylglyoxime solutions) placing them in separate dedicated dropper solution bottles. Before testing, you must thoroughly clean the metal in order for the electrolytic deposit to take place. You may use nonmetallic hand scrubbing pads or 320 to 600 grit “crocus cloth” to remove deposits and corrosion products (thermal oxide).

Figure 5-2. Wiring assembly schematic.
Figure 5-2. Wiring assembly schematic.

Connect the alligator clip of the wiring assembly to the bare metal being tested. Place one drop of a 0.05 percent reagent grade ammonium fluoride solution in deionized water on the center of a 1 inch × 1 inch sheet of filter paper. Lay the moistened filter paper over the bare metal alloy being tested. Firmly press the end of the aluminum rod over the center of the moist paper. Maintain connection for 10 seconds while rocking the aluminum rod on the filter paper. Ensure that the light emitting diode (LED) remains lit (indicating good electrical contact and current flow) during this period. Disconnect the wiring assembly and set it aside. Remove the filter paper and examine it to determine that a light spot appears where the connection was made.

Figure 5-3. Electrochemical test results, Inconel and stainless steel alloys.
Figure 5-3. Electrochemical test results, Inconel and stainless steel alloys.

Deposit one drop of 1.0 percent solution of reagent grade dimethylglyoxime in ethyl alcohol on the filter paper (same side that was in contact with the test metal). A bright, distinctly pink spot will appear within seconds on the filter paper if the metal being tested is Inconel. A brown spot will appear if the test metal is stainless steel. Some stainless steel alloys may leave a very light pink color. However, the shade and depth of color will be far less than would appear for Inconel. For flat surfaces, the test spot will be circular while for curved surfaces, such as the outside of a tube or pipe, the test spot may appear as a streak. (Refer to Figure 5-3 for sample test results.) This procedure should not be used in the heat affected zone of weldments or on nickel coated surfaces.

Flight Mechanic Recommends

Rod Machado's Private Pilot Handbook -Flight Literacy recommends Rod Machado's products because he takes what is normally dry and tedious and transforms it with his characteristic humor, helping to keep you engaged and to retain the information longer. (see all of Rod Machado's Products).
   
-->