400 alloy, a nickel-copper alloy, has greater corrosion resistance than commercially pure nickel and greater oxidation resistance than refined copper alloys. Type 400 shows outstanding chloride stress corrosion resistance. It exhibits resistance to salts and most bases in lower temperatures. It is not recommended to use alloy 400 in nitric or nitrous acids that are extremely oxidizing, although alloy 400 does perform well in hydrochloric acid, sulfuric acid, and other reducing acids. Type 400 is extremely cold formable. Alloy 400 is commonly used in aqueous environments, especially sea water and brackish water.