Alloy 400 is a nickel-copper alloy that resists seawater, steam, salt solutions, and caustics. This alloy is easily welded and has good mechanical strength with excellent resistance to stress-corrosion cracking. Alloy 400 is resistant to de-aerated hydrochloric and hydrofluoric acids. The nickel-copper alloy has good mechanical properties from sub-zero temperatures to 1,000 °F. The mechanical properties can be increased for applications requiring higher strength by applying cold work after the final annealing operation.