Identify the aluminium parts in your vehicle that you want to coat with chrome and take them out of the car. Place them on a table and use aluminium polish to clean them. You should make sure that there is no hint of grease or any other form of impurity on the aluminium parts, and if there is, use a vapour degreaser to remove it.
Make a sodium hydroxide mild solution and dip first aluminium part in it. The corroded part on the surface of the aluminium will toughen up, this will help in the plating of the chrome later on.
Use a mild sand paper to smoothen the surface of the aluminium part if it becomes too rough. Do not go too hard on as to remove the shine from the surface of the metal. Prepare a mixture of dioxide solution and put the objects to be plated in it for about 15 minutes. The purpose of etching solution is to roughen up the corroded surface even more.
Take the objects out of the solution and place them on dry cloth. After drying them out rinse them with clean water and then put them in a solution of mild sulphuric acid. Connect two aluminium parts with the terminals of the battery and put them in the solution of the acid. The temperature of the mixture should be around the 115 degree Fahrenheit mark.
Turn on the switch so that the DC current flows through the circuit. Dip the aluminium in liquid copper bath and then put it in a liquid nickel strike solution.
Wait for the parts to dry and then rinse them again with distilled water. Prepare a hex chromate solution by following the instructions on the box. Put the aluminium object in the solution and connect both electrodes. The plating will occur in about 2-3 hours time.