I cooked on a charbroiler for about 8 or 9 years and had the duty of, every Thursday, cleaning the charbroiler.
The charbroiler was proably about fifteen years old by the time I left. It was still in great shape and the only thing we ever had to replace on it was the ceramic blocks on the bottom because they'd sometimes crack (rarely, though). To clean it, I would take a thick handled butter knife and scrape each individual grate until it was free of most debris. They also make nice brushes to keep the tidy during cooking times.
Maybe you could sandblast one and see what happens? Also, we rotated our grates each week to ensure even wear and use.