Quote:
Originally Posted by ROBERT CROSS
Rust is not all that bad all the time...it forms an oxide which can coat & protect, corrosion is reactive and can destroy the metal.
It's better to coat rust with a converter, that works much better in preventing the spread.
Bob
🇺🇸
POI...our step is no worse now than it was 15yrs ago when I repaired the support arm.
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Not exactly...
Aluminum that is exposed to oxygen readily forms a passivation layer that encapsulates and protects the substrate material from further oxidative corrosion. For exposed steel to develop a passivation like this requires a strictly controlled environment in which heat and minerals are applied in specific amounts and sequence (this is the process utilized to ‘blue’ the metal of firearms).
Such controls would never happen on a road traveled trailer frame consisting of mild HRPO steel.
Rust is permeable to air and water, and the resulting iron oxides take up more volume than the original metal. These hydroxides do not adhere to the bulk metal and actually act like a sponge that absorbs additional moisture and minerals. As they form and flake off from the surface, fresh iron is exposed, and the corrosion process continues until all of the iron is consumed—thus the nomenclature used in the auto body shop industry ’cancer’. Therefore, the interior metallic iron beneath a rust layer continues to corrode.
Rust prevention thus requires coatings that preclude rust formation. This could be through the use of pickling, continual application of a viscous volatile petroleum evaporating coating like wd40, or sanding and repainting exposed metal to maintain a protective atmospheric seal.
In short, it’s a good idea to maintain the paint on your frame.
Unfortunately, airstream really doesn’t do a great job of prepping their steel frames before applying the paint. It is pretty common to see newer coaches that have rust forming all over the exposed areas of the a-frame.