On 23/07/16 21:53, ss wrote:
On 23/07/2016 18:16, Archibald Tarquin Blenkinsopp wrote:
Phosphoric acid will then convert the rust to something paint
friendly

Can be bought cheaply on ebay.

Iron phosphate.

Tough and stable.

"It can be used in steel and metal manufacturing processes. When bonded
to a metal surface, iron phosphate prevents further oxidation of the
metal. Its presence is partially responsible for the corrosion
resistance of the Iron pillar of Delhi.

Iron phosphate coatings are also primarily used as base coatings for
paint in order to increase adhesion to the iron or steel substrate, and
is often used in rustproofing as well. It can also be used for bonding
fabrics, wood, and other materials to these surfaces as well. Iron
phosphate coatings are usually applied as part of a painting or powder
coating process."

https://en.wikipedia.org/wiki/Iron(III)_phosphate

In fact rusty iron/steel that has been phosphated with acid will
probably be more resistant to corrosion than bare metal


--
"When a true genius appears in the world, you may know him by this sign,
that the dunces are all in confederacy against him."

Jonathan Swift.