In case of fatigue testing of steels, what would be a good way to protect fracture surface from rusting for up to 15 days? These are fatigue test samples for 1 mm thick IF and DP steels. Minimum cross section of samples (surface area after fracture) is 1 mm (thickness) x 5 mm (width).
Hi Kanwer, this is Frank from HZDR. How are you? For your application, isn't storage in a desiccator sufficient, in particular if you do the fatigue testing in air? Perhaps you might put fresh silica in the lower vessel of the desiccator. Otherwise you may spray a suitable acid-free oil onto the fracture surfaces. E.g. Reichelt spray oil 88. Please make a trial first. Best wishes and regards, Frank
Hello Frank. Many thanks for your reply. I am doing good and wish the same for you :)
Unfortunately, desiccator is not working well for my case. Queue for SEM imaging is long and by the time its my turn a large portion of the surface is rusted. I will definitely search for an acid-free oil equivalent to Reichelt spray oil 88. I believe that this will do the trick for me. Shall keep you informed. Many thanks again and wishes - Kanwer
Kanwer, Oil should work. Take fresh silica and/or heat till it turns blue before use. Or else, slightly high end desiccators with humidity control are available in Indian market. Cost depends upon size and the number of racks. You can buy one. I have some of the fracture surfaces kept in normal desiccator (without any oil coating) and they are all in good condition. You have to periodically change/heat the silica. BYW, the most important thing is that how you are break opening the tested specimen (if it is not separated in to two pieces naturally during course of testing). I suspect you are using liquid nitrogen to open-up the remaining ligament or employing a cutting method that uses coolant. Avoid these two methods, if you cannot go to SEM immediately. However much care you take, there will be moisture entrapment and the surface will corrode soon. Use simple hack-saw (I know it will be laborious) without any coolant. If at all you have to use liquid nitrogen/slow speed cutter with coolant, use hot air blower to dry the specimen after cleaning with alcohol/acetone.
Dear Dr Shiva, many thanks for your reply. As sugggested, I will look for a high end desiccator for my work and will also avoid using liquid nitrogen for separating two halves of samples, which have not broken after testing. Thank you again - Kanwar
I used sodium chlorate in desiccator. It kept my aluminium 7000x series fracture surfaces from oxidation for over a year. Good luck
Desiccators will always work but as a freshly fractured steel surface is highly active and extremely susceptible to corrosion, I have always left my broken steel samples in acetone, which both protects them and cleans them too!
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