Rustyco rust solvent

The text below is from the site of the manufaturer:

RUSTYCO ® RUST-SOLVENT is a unique rust remover. It removes all rust from all joints and cracks, pore-deep, from steel, stainless steel and most ferrous metals, without having to resort to blasting or sanding. It is not a converter. Gives metal a greyish anti-corrosion layer on a surface that has been microscopically cleaned; the ideal base for primers and paints. 
Treat your metal as if it were new. RUSTYCO ® is a high-grade concentrate, soluble in water and economical, especially for large objects. One litre of RUSTYCO ® is enough for a powerful 20-litre rust-removing dip that can be reused, until it has turned dark/black in colour.

RUSTYCO ® does not affect the base material. It is safe to use. It does not damage varnish, plastic, wood, rubber, vinyl, stainless steel, aluminium, copper, glass, chromium, etc.
The product does not produce any noxious fumes, is non-toxic, non-combustible, biodegradable and environmentally friendly.

INSTRUCTIONS FOR USE:
First, remove any loose rust, dirt, grease and oil.
Prepare a solution in water, e.g. in a plastic bucket or container.
Add 50 ml (= 5 caps) of RUSTYCO ® per litre of water.
Add more RUSTYCO ® for high levels of rust.
This will also prolong the life of the solution. Fully submerge the object in the rust-removing dip (at least 30 minutes). You may need 72 hours to remove high levels of rust. Take the objects out of the solution on a regular basis, brush off any loose rust and rinse with water. This will advance and speed up the process. 
By heating up the solution (up to a maximum of 65oC), all rust will disappear very quickly.
Submerge for another 5 minutes and leave to dry in order to give the object a temporary anti-corrosion layer after the process.
It is now ready for further treatment.

Use RUSTYCO ®-GEL to remove rust from objects that cannot be submerged.

For more information, see Rustyco