Dear Alexander

I think it is better to add microstructural studies using SEM/EDS to your investigation. Results of Salt spray and fog tests according to ASTM B117 are mostly comparatively. besides, I strongly suggest to have electrochemical corrosion testing in your researches for measuring corrosion rate. However you should be aware that these methods also have their own difficulties for Al alloys due to passivation.

Good luck.

Dear Reza,

Thank you for your answer.

Dear Dr. Alexander Shinkaryov,

the experimental trials that I generally used are electrochemical tests and free corrosion ones at various corrosion times.

The electrochemical tests consist of potentiodynamic DC polarizations (anodic and cathodic) through which the corrosion average speed rate and the localized corrosion sensitivity are evaluated.

The free corrosion tests are performed for time ranges from 120 to 1440 hours.

Through this type of test, the weight loss are measured by summing the content rate of the aluminium in the solution (under the form of soluble corrosion products) with the amount of Al corrosion products adhering to the metal substrate and dissolved using a proper method which allows one to keep the metal matrix steady. The quantity determination of the aluminium is carried out by atomic absorption spectrophotometer.

The corrosion products are characterised via X-ray photoelectron spectrometry and Auger spectrophotometry. The XPS analyses are carried out using Mg Ka radiation (E=l253.6 eV) as excitation source and the spectra are obtained at a vacuum better then 10-7 mbar and detection angle perpendicular to the surface. The C1s peak (Binding Energy, B.E. = 284.8 eV) is used ad internal standard which persisted as it is due to the surface contamination, which is used to evaluate and compensate the charging ef­fects of the specimens.

Some Auger mapping is also carried out on corroded test samples to model the surface corresponding to the areas where localized corrosion has occurred.

Via free corrosion tests we obtain information concerning the corrosion morphology and intensity using a metallographic microscope combined with an image analysis system; the occurrence of segregations, disbondments of the alloy following the localized corrosion are also tested through X-ray micro diffractometry. Other data were obtained by means of an atomic force microscope working in contact mode with an Si3N4 tip on a 70x70micrometer area.

Best regards, Pierluigi Traverso

The corosion on steel ,can reaction some year.

Thank you for aswering

Depends on the test object that we are examining, and the time of use