The authoritative public forum
  for Metal Finishing since 1989
-----

Chemistry - rusting

Hello sirs,

I'm a high school student. I'm doing my chemistry assignment. I don't understand and I can't find information on the net

1. I can't find the reason for silicone prevents rust because I find silicone in the contains of some coating for preventing rust.

2. Why does normal paint has toluene as major? what's the effect of this in the paint? what does it do?

Thank you very much,

Wendy L.
- Sydney, NSW, Australia
2003

---

You really do speak a different language "down under". You do mean silicone not silicon? Silicone is an organic compound and can certainly exclude water and oxygen from touching a metal surface, thus keeping it from oxidizing. I don't think I agree that 'normal paint' has toluene as a major ingredient; but in general and on an easy level, you need something to wet the paint that will evaporate so it dries.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003

Perform a web search using the following keywords: citric acid passivation citric acid pickling citric acid descaling citric acid cleaning

Toby Padfield
- Michigan
2003

---

Silicone is a polymeric chain of silicon and oxygen. It can be made into a range of products from a liquid through to a full blown quite hard solid. The thing about liquid silicones is that they are water repellant and consequently, when they are put onto a material like clean steel, they will repel any water that may cause corrosion (or rusting). Hence liquid silicones can act as a barrier layer. As far as toluene in paint is concerned, lots of paint do (or did) contain organic solvents such as toluene as they assist in the drying of the paint as well as acting as a good solvent for same of the chemicals in the paint. More modern paints use water and water-miscible solvents as the main solvent. These modern paints have overcome the problems of long drying times associated with the older water based systems and they have also got round the strong aroma (some may say stink!) and nasty side effects of organic solvents.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2003