You don't mention anything about temperature, degree of aeration, etc. so I can only offer limited advice. Alloy 904L has some application for HCl service but only for concentrations less than 3%. Depending on the temperature and other specifics to your application, an alloy in the Hastelloy C family might work. The only metal that offers practically complete resistance to concentrated HCl is tantalum. You might be better off moving away from metals entirely and using a glass or plastic.