Treating carbon steel tubing includes contacting the carbon steel tubing with a first treatment solution including a salt; corroding the carbon steel tubing with the salt to yield a corroded surface on the carbon steel tubing; contacting the corroded surface on the carbon steel tubing with a second treatment solution comprising sulfide ions; and forming an iron sulfide layer on the corroded surface of the carbon steel tubing by chemically bonding the sulfide ions in the second treatment solution with iron in the carbon steel tubing. In some cases, the first treatment solution also includes sulfide ions, and the iron sulfide layer is formed by contacting the carbon steel tubing with the first treatment solution.