Just goes to show that you have to be on guard all the time. Now I will be very reluctant to use anything at all. Corrosion free is applied every 18 months but at a much higher cost $149.00 (Canada) and I thought Krown was to expensive at $129.00 for a little pickup.ust goes to show that you have to be on guard all the time. Now I will be very reluctant to use anything at all. Corrosion free is applied every 18 months but at a much higher cost $149.00 (Canada) and I thought Krown was to expensive at $129.00 for a little pickup.