Maintenance of a steel bicycle frame
Let’s start by defining some key terms to understand why a steel bicycle frame needs to be maintained.
Rust, corrosion, steel alloys, vent holes and frame saver (rust and corrosion protectors for steel).
Rust:
It is the compound that arises by combining oxygen with a metal, it is called basic oxide, they react with water to form hydroxides, they are the bases, hence their name.
It is produced on the surface layer of metals creating a reddish or coppery surface.
Generally with a thorough cleaning we can remove this oxide layer by polishing or sanding.
Rust is the first step before corrosion, by cleaning it properly there will be no corrosion.
Corrosion:
This is when the metal starts to deteriorate structurally, not just superficially as in the case of rust.
In this case it can compromise the reliability of the structure and its safety, and premature breakage may occur.
Steel alloys:
Steel arises from combining iron with carbon, and this is the basis for many alloys for bicycle frames, depending on the manufacturer.
These alloys give bicycles specific properties that have evolved a lot since the appearance of the first frames.
The most common elements with which steel is usually combined are: Silicon, Manganese, Chromium, Molybdenum, Vanadium, Phosphorus and a long etcetera depending on the manufacturer, which carefully keep their components and proportions just like a chef with his recipes.
A common alloy used in quality bicycles is 25CrMo4.
Vent holes:
They are made during the construction of the frame, their mission is to prevent moisture or substances that arise during manufacture from remaining inside the tubes, thus preventing subsequent rusting and corrosion.
Each tube has two vent holes for proper ventilation. Normally they are not visible because they are made in the joints between the tubes, but if we look closely the sheaths usually have vent holes visible.
Frame saver (rust protectors):
There are a multitude of protective products and rust converters, there are many specialties that use this type of products: construction, automotive, aeronautics and of course in the bicycle industry among others.
At this point we must differentiate between converters and protectors.
The converters react with the rust creating a protective layer, whereas the protectors create a layer preventing rust from being deposited or generated.
We can find protectants that are environmentally friendly for similar or even cheaper prices than some chemical protectants.
Linseed oil can also be used to protect but is a little more difficult to apply and perishable.
The products used in the maintenance of steel frames are the protectors, as the converters are used when rust has already been generated.
After defining these concepts we can know a little more about the importance of maintaining the steel frame of a bicycle.
Depending on the climate in which we find ourselves, maintenance will be carried out between different periods of time, but we should not be alarmed because it will be a tedious or time-consuming task.
In dry climates and with a regular use of our beloved bike this work would be done once every 2 years and in humid or coastal climates we will do it once a year.
I already mentioned the different products to apply, in my case when I finish making a frame and it is painted, I then apply the product through the vent holes, the easiest way is to use a product that comes in an aerosol with a fine sleeve for its application.
The vent holes through which we are going to apply the product are 2 in the head tube, we will be protecting the head tube, top tube and down tube.
Seat tube we find another vent hole that communicates with the top tube, we apply in this vent hole and in the seat tube itself.
Bottom bracket, we will find 4 vent holes, one communicates with the down tube, another communicates with the seat tube and two that communicate with the lower chain stays one for each of them. The product must be applied to all of them.
The chain stays must have another vent hole for each of them and finally the seat stays have two in sight. The product must also be applied to these small vent holes.
This maintenance operation should also be applied if we have a steel fork, it can be applied in the main tube of the steering and in each of the respective sheaths of the fork, it would be applied in the same way as in the seat stays.
When we are applying the product it is best to protect the areas where the product can come out with a cotton cloth that does not leave residue and remove any excess product. This way we will not dirty the whole working area.
Vent holes head tube 
Vent holes seat tube Vent holes bottom bracket Vent holes chain stays Vent holes seat stays
If you don’t have the necessary tools or simply don’t want to carry out this maintenance yourself, take your bike to your usual mechanic to have it done.
Take care of your bike so that it takes care of you!
Thanks for the useful information. In my experience, nothing can be completely rustproof. A good steel frame will outlast any other material, so let’s pay extra attention to protecting this material well. Using any kind of metal lubricant inside the tubes will help prolong the life of your steel frame. The seat tube and bottom rack are where rust is fastest, as moisture easily penetrates them. Always remember to lubricate them, especially after a wet ride, as the lubricant can easily wash off from tire spray and water seeping between the crevices.
Thanks Patrick for sharing your experiences and the extra information.