If it has a 12 year no penetrative corrosion warranty then you could argue that for the chassis to have penetrated to a dangerous extent seven weeks later then it must already have suffered penetrative corrosion during the 12 years. However, I have not heard of that working in a court case and it will depend on the wording of the corrosion warranty. Such things as missing an annual inspection at a Nissan dealer can void it entirely. Unless a manufacturer warrants a vehicle otherwise or the vehicle is subject to a safety recall, it is only liable for major faults for six years and this truck is so far past the six years that a judge might not rule in your favour.