The effect of pH on corrosion metals
INTRODUCTION:
Corrosion is the degradation of metal due to chemical or electrochemical reaction within its environment converting it to a more stable form, often an oxide. This process is called oxidation, which can weaken and damage metal structures. pH scale is used to measure acidity or alkanity of a substance or object. Corrosion rates are significantly influenced by the pH of surrounding environments. This has impacted many metals structure for example pipelines, ships and metal structures. The scientific principle behind this investigation is that acids speed up corrosion making it easier for metal to react and break down.
AIM:
To investigate how the pH levels affect the rate or degree of metal corrosion.
HYPOTHESIS:
If a metal exposed to a pH below 7, then it will show more corrosion because acidic solution increase the rate of metal breakdown.
METHOD:
Clean each metal sample with sandpaper to remove any existing oxide layer.
Label five beakers as pH 2, 4, 7, 9, and 12.
Measure and pour 80 mL of each pH-adjusted solution into the respective beakers.
Place an identical piece of the same metal (e.g. iron nail) into each beaker.
Leave the samples undisturbed for 48 hours at room temperature.
After 48 hours, remove and observe the degree of corrosion on each metal sample.
Record any visual changes (rust, color, texture).
Rate corrosion qualitatively (e.g., none, low, moderate, severe) or measure mass loss if a scale is available.
RESULTS:
pH Levels Observation on Iron Sample Corrosion Levels
2 Heavy rust, reddish layer Severe
4 Moderate rusting Moderate
7 Slight tarnish, little rust Low
9 Very little visible change Minimal
12 Slight darkening Low to Moderate
DISCUSSION:
The results suggest that corrosion was most sever in highly acidic conditions (pH 2) and decreased as the pH approached neutral and slightly basic. Slight corrosion reappeared at very high pH (pH 12), possibly due to alkaline reaction with the metal surface. This supports the principle that that acids speed up corrosion making it easier for metal to react. The results may have been affected by uncontrolled variable such as uneven cleaning of metal sample before the experiment which may have left some oxide layers or oils on certain samples, which could affect how much they corrode. Improvement to this potential error can include using fine sanding paper. This is because sanding removes any oxide or protective layers.
CONCLUSION:
This experiment supports the hypothesis that a more acidic based solution will how the most corrosion on metal. This aligns with the theory that acids speed up corrosion on metal. Real-world applications include building metal structures, pipelines and battery and electronics manufactures. Understanding show pH levels effect corrosion in metal is crucial in high safety and engineering designs.
