Stainless Steel vs Aluminium

      Stainless Steel          Aluminium
Looking at strength, stainless steel is much stronger then aluminium. Aluminium is definitely not so strong like stainless steel but it is also one third of the weight of SS, and that is why it is used in aircrafts. 
Due to the components used in stainless steel, this is the most resistant product to corrosion. Expectancy to last between 15-20 years. Aluminium may corrode rapidly with catastrophic results.
Thermal conductivity of stainless steel is not very good. Aluminium has a much better thermal conductivity and that is why it is used in car radiators and air-conditioning units.
Stainless steel is hard, which is making it difficult to form. Aluminium is soft and easy to form.
Stainless steel is easy to weld. Aluminium can be difficult to welding.
Stainless steel can be used in very high temperature. Aluminium can become very soft at around 400 degrees.
Electrical conductivity for stainless steel is poor. Electrical conductivity for aluminium is very good.
Stainless steel is much stronger then aluminium.  ————
Stainless steel is no reacting with food. Aluminium can react with food which can affect colour and flavour.
Expensive but in the long term projects can proof to be much cheaper. Typically cheaper

Looking at this table you can see that there are good and less good things about both products and the final decision which to use it, will depend on your project.

For viscosity measurements we will always recommend flow cups made from stainless steel which are more resistant to temperature, corrosion and accidental damage.