Regarding to your concern . After our careful investigation with K.Surin Executive manager of Mitsu Sathorn.
He informed us, He already explained customer about this issue as follow :
The rust in car brake, Its may potential depending on moisture as The disc FR brake made from metal figure
and install with Invisible area. Normally The rust dose not effect for use. If customer need to remove the rust,
technician could use chemical cleaners for remove it, Therefore It has the cost as this impact not covered in normal warranty.
Please kindly explain this detail to customer