Corrosion Inhibition of Magnesium by Anodizing In Safe and Unsafe Alkaline Electrolytes
Mahmoud Abbas1, Salah Salman2, Shaimaa Ali Abou El Ela3
1Mahmoud Abbas, Metallurgical and Materials Engineering Department ,Faculty of Petroleum and Mining Engineering ,suez ,Egypt, Suez University.
2Salah Salman, Mining & Petroleum Engineering Department ,Cairo , Egypt , Faculty of Engineering Al-Azhar University.
3Shaimaa Ali Abou El Ela, Metallurgical and Materials Engineering Department ,Faculty of Petroleum and Mining Engineering ,suez ,Egypt, Suez University.
Manuscript received on November 11, 2019. | Revised Manuscript received on November 20 2019. | Manuscript published on 30 November, 2019. | PP: 11479-11484 | Volume-8 Issue-4, November 2019. | Retrieval Number: D4235118419/2019©BEIESP | DOI: 10.35940/ijrte.D4235.118419
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Abstract: Magnesium has high strength to weight ratio , good machinability , high creep stress and high impact resistance . Such properties make the magnesium an excellent choice in many applications . Disadvantages of magnesium represented in low corrosion resistance in most environments and ignites easily in air . Surface modification techniques which are used to improve surface properities of Magnesium are conversion surface treatments like chromating , phosphating , galvanizing electroplating such as Cu , Zn , Ni , Cr , electroless metal plating and cladding by Aluminum foil . Anodizing in an electrolyte (with pH>12) is considered a passivation process that produces chemical stable protective oxide film on magnesium surface . Usually unsafe electrolytes such as KOH are frequently used . Anodizing of commercial magnesium (ASTM 9980A) was carried out in 3M KOH(unsafe) , 1M Na2SiO3 and 0.6M K2SiO3(safe) electrolytes for time periods ranging from 10 to 50 minutes at constant voltage of 5V .The anode was magnesium specimen where the cathode was stainless steel type AISI 304 . Energy Dispersive X-Ray(EDX) and X Ray Diffraction (XRD) approved that magnesium Oxide (MgO) is the anodic film when using 3M potassium hydroxide electrolyte and a magnesium Silicate with a glassy morphology formed in the anodic film using safe electrolytes of 0.6M potassium silicate and 1M sodium silicate . Maximum film thickness reaches to 46 , 27,47 μm after anodizing at 30 min using 3M potassium hydroxide ,1M Sodium silicate , 0.6M Potassium Silicate respectively . It was found that the corrosion rate of commercially pure magnesium decreased from 37 to 7 , 2.2 , 1.3 mpy when using 3M potassium hydroxide , 1M sodium silicate , 0.6M potassium silicate respectively . At the same time the contact angle increases from 70 degrees to 114o, 105o , 113o degrees using the same electrolytes . An increase in microhardness of the anodic films was observed in 3M potassium hydroxide , 1M sodium silicate and 1M potassium silicate respectively . The adhesion of the anodic film measures according to ASTM D3359 method 13 for thickness <125 μm was classified in 3B which denote that the amount of the layer released by the adhesive tape lies from 5-15% of the formed layers using the three electrolytes.
Keywords: Anodizing , Corrosion , Corrosion Inhibition , Alkaline Solutions.
Scope of the Article: Smart Solutions – Wearable Sensors and Smart Glasses.