The steps of the process
Rust removal happens in an acid bath at about 50° Celsius. There are a lot of prejudice about it. You can read on the internet about acid that remains in the seams and cause rust long after the car is tightly lacqeured. These stories are not complete nonsence, but only when hydrochloric acid is used.
When a body is not completely neutralised and passivated, there might be some hydrochloric acid molecules be left behind on hard to reach places. In a later stage these molecules can be re-activated by damp or moist air and cause rust and all troubles along with it. Therefore, to solve this problem, Autobeitserij Holland uses Phorphoric acid. When Phorphoric acid dries (by air or forced by heat) it is chemically changed into iron phosphate. This is an irreversible chemical reaction. Iron phosfate will never become an acid again, not even when it gets wet.
This iron phosphate has slightly protective charecteristics, to be compared with the thin oxide layer of aluminium, which prevents from rust. Identified by the whitish touch on the body