What is the final cleaning step in the increasing order of aggressiveness?

The final cleaning step in the increasing order of aggressiveness is sanding. This method is considered an aggressive cleaning technique, as it physically abrades the surface of the container to remove contaminants, corrosion, or paint. Sanding is often used as a preparatory step before painting or sealing containers, ensuring that the surface is as clean as possible.

In contrast, the other cleaning methods listed are less aggressive. Water washing and detergent washing typically involve the application of liquids that dissolve and remove dirt and grime but do not impact the underlying material as significantly as sanding. These methods provide a thorough cleaning without altering the surface's structure. Steam cleaning is also a gentler approach, utilizing high-temperature steam to sanitize and remove debris without the abrasive action of sanding. As a result, these techniques are generally used before sanding in a cleaning process, where the objective is to first remove loose dirt and grime, followed by more aggressive techniques if necessary. Therefore, sanding represents the final, most aggressive step in container cleaning methods.