Hypothesis, Aim and revised equipment/method

Aim- To investigate the effect of salt concentration on corrosion rate of magnesium and zinc in stagnant and aerated solutions. Hypothesis- If the concentration of salt in solution is increased, then the corrosion rate for both magnesium and zinc will increase. If the salt concentration remains the same, though the solution is aerated, then the corrosion rate will increase again for both metals. Materials- 50g Sodium Chloride 20cm Magnesium Strips 20cm Zinc Strips Metal Scour Dissolved Oxygen Probe Marking Pen Distilled water Sensitive weight scales Test Tube Rack 12 x Test tubes Mortar and Pestle Procedure- 1) A test tube rack was obtained and three of the test tubes were numbered and placed chronologically in the rack. A table was drawn to record the results, with the numbers used to indicate each test tube. 2) 10mL of distilled water was added to each test tube, making sure not to disturb the water more than absolutely necessary. 3) Using the mortar and pestle, the NaCl was crushed into a consistent fine powder. 1g of the powdered sodium chloride was placed into test tube number 1, 0.5g into test tube number 2 and 3g into test tube number 3. Each test tube was swirled slightly to dissolve. 4) The dissolved oxygen content was then measured for each of the solutions in the test tubes and the results recorded. 5) 3 x 1cm long magnesium strips were scoured in order to remove the oxide present, before being weighed and measure (length, width and depth) and added to each of the three test tubes respectively, remembering to place the correctly weighing strip in the corresponding tube. Leave for three days, recording as many observations as possible. 3) Repeat above steps with zinc. 4) Repeat previous tests for both Zinc and Magnesium, though before doing so ensure water is aerated. Add required amounts of salt before testing dissolved oxygen levels. 5) EXTENSION: If there is an appropriate amount of time, add both magnesium and zinc to the same test tube and compare any differences in corrosion rate.