I'm thinking of treating my steel frame, in order to protect it from rust.
First, I would clean the tubes inside, with a non-aggressive solvent similar to avgas. It's not exactly avgas, as it's composed of just:
- 92% Hexane and isomers (<5% n-hexane);
- 8% 1,2-Dichloropropane.
In Italy it's sold as a cleaning agent, and called avio.
An alternative would be isopropyl alcohol (C3H8O), but it's very tough to find somebody that stocks it here in Italy.
Second, I would apply a rust removal product. Many rust removers use high concentrations of phosphoric acid, but I'd rather opt for FERTAN.
FERTAN is a water based complex tannic acid product. In contrast to common rust removers, it has just a tiny quantity of phosphoric acid. It therefore seems a safer alternative, but it should be pretty effective nevertheless.
Most rust removal products use high concentrations of phosphoric acid. If the phosphoric acid is not completely consumed by its reaction with the oxides on the surface being treated and the surface itself then it will attack the metal and any other surfacing products that are applied. It is obviously very difficult to calculate the amount of acid to apply as it depends on the degree of rusting, the type of oxides present. So these products need to be applied in excess. The treated surface should then be power washed to remove all excess before applying finishing layers.
This is likely to remove the layer of tertiary iron phosphates that provide the protection and allow water through to the surface of the metal. But if it is not done then the acid remains to attack the finishing coats.
Fertan works differently. It is composed principally of:
pyrogallic acid glucosides / ellagic acid glucosides (molecular weight 270 - 2000)
phosphates of bivalent transition metals such as Zinc and Manganese
Zinc and manganese nitrates.
Fertan, when taken from the container is a complex chemical solution which is in an equilibrium state, meaning that it will not change until other chemicals come into contact with it. It is so stable that it will remain unchanging for twenty years. We have old samples that we test annually for effeciveness.
Once iron oxides are detected the liquid uses up its initial tiny percentage of phosphoric acid. Then it generates a tiny amount more. It needs a tiny percentage of the acid to be stable. If that is used up by attacking iron oxide then Fertan will generate more. The process is repeated until no rust is left. So at no time is there a large quantity of acid present.
Finally, I would spray an anti-corrosion product, like ACF-50. I like ACF-50 because it doesn't contain any wax or silicon additives. So it should dry to a clean film, rather than to a sticky substance like e.g. J.P. Weigle's Frame Saver.
I would repeat this treatment yearly--I live in a wet and muddy region, especially in late winter/spring, and I often need to wash thoroughly my bike!
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Thread: Anti-rust treatment for steel