1. Mechanical derusting: Scrape the rusted surface with tools such as wire brush and copper brush, and remove the derusting skin to make the metal surface smooth again.

2. Chemical derusting: Soak or spray it on the corroded surface with acid or alkali solution, so that the rust layer reacts chemically with the steel surface and corrodes the rust layer, thus realizing derusting.

It should be noted that before rust removal, the interior of the anaerobic tank must be inspected or tested regularly to ensure that the tank wall structure is firm and there is no corrosion and water leakage.