Stone chip damages and corrosion from accumulated dirt around the base of the B-pillar is a common problem on the Ka.  The area is a design problem, in that the base of the door can sit inside the line of the B-pillar so debris flicks up and hits exposed paint work head on. 

 

As soon as you catch corrosion in this area, get it seen to at a bodyshop.  You can fit protectors, however be careful that moisture does not sit underneath the protector and corrode the Ka whilst hidden from view.