Visually, the two metals are very similar. However, there are some key points that can help you differentiate between the two.
- Appearance: Steel, particularly stainless steel, has a metallic luster where the metal appears shinier. Aluminum usually is devoid of a lack of luster and visually can be characterized as a dull grey.
- Weight: Steel is 2.5 times more dense than aluminum. If you have two parts made of aluminum and steel, the steel part will be considerably more heavy.
My favorite test that doesn’t involve any special equipment is to visually score the two metals using a common house key. House keys are typically made of brass which is harder than aluminum but less hard than steel. Depending on which piece can be scratched, you’ve identified the aluminum part!