Lye won't hurt the plating, so neither should lye-based oven cleaner. If you have the ability to regulate and monitor the temperature of your grill to keep it, say, under 500° you should be OK. Some people are looking for a blackening effect using charcoal grills on bare iron, which is not what you would want with your freshly cleaned nickel. If you're using the grill to avoid the smell inside the house, keeping your oven temp just below the smoke point of the oil or fat will minimize the odor. Refined grapeseed oil would be a good choice, as it has a 450° smoke point. Crack a window to help your kitchen exhaust fan operate more efficiently. Bear in mind with plated pieces, you only need to concentrate on seasoning the bare iron of the cooking surface; just wiping the areas on the outside where plating is worn with some of your seasoning oil once the pan is dry should be sufficient for rust prevention.