To remove scratches from aluminium channels, you can try the following methods:

• Sandpaper: Begin with a fine-grit sandpaper, such as 320-grit, and gently rub the scratch in a circular motion. Work your way up to a finer-grit sandpaper, such as 600-grit, until the scratch is no longer visible.
• Aluminum polish: Apply a small amount of aluminum polish to the scratched area and rub with a soft cloth until the scratch is no longer visible. Be sure to follow the manufacturer’s instructions for the polish you are using.
• Baking soda: Make a paste of baking soda and water and apply it to the scratched area. Rub gently with a soft cloth, then rinse with water and dry.
• Vinegar and water: Mix equal parts white vinegar and water and apply to the scratched area. Rub gently with a soft cloth, then rinse with water and dry.

It’s important to note that these methods may not work on deep scratches or gouges, and may not completely restore the appearance of the handrail. In some cases, it may be necessary to replace the damaged section of the handrail.