I had the same question as Charles Andrews. Paint can protect the exterior from rusting but does nothing for the interior of the tubing.
Examples:
1. Several years ago a friend bought a lugless 1950s-60s mystery French constructeur bike at a swap meet. The frame was made of extremely thin tubing, nothing fancy but well made.
When he stripped the rattle can paint off he found serious pin holing in the seat stays and fork blades. He had a new fork built plus the seat stays replaced.
2. I bought a classic mid 60s wall hanger a few years back. The paint and chrome were just about perfect. I inspected the bike when it arrived but let it set for over a year before reassembling it.
When I went to put the seatpost in I noticed some very large rust flakes on it. I looked down the seat tube and they whole inside was crusted with large rust scale!
The frame is made of light gage Reynolds 531 so there may be a lot of internal rust in the other tubes too! It's going to remain a wall hanger.
3. I've seen a number of old frames with rusted out seat stays at a local frame builder's shop. Many of them looked good until he removed the paint. He uses a chemical paint stripper but sand blasts the frames if there's surface rust. Thats when pinholes really blow through!
Internal rust on chrome plated frames may be the result of improper cleaning after the plating operations. Corrosive chemicals can remain inside the tubes.
In a humid climate, even if the exterior is well maintained, moisture can get inside the tubes over time and cause rust. It even gets in through the small vent holes in the forks and stays. Near the ocean, that moisture can be salt laden too.
One other consideration, a few years ago there was a red, black and yellow Raleigh Team Pro frame "floating" around on eBay. It appeared to have been under water for some time. Either the seller was naive or nefarious but it kept being relisted with glowing descriptions!
That brings up the possibility that internally rusted bike frames may have been in a flood at one time???
Chas. Colerich Oakland, CA USA
Kurt Sperry wrote:
> How many people here have personally as opposed to it happening to a
> friend, cousin etc. had classic steel frames experience an actual
> structural failure due solely to rust? I've never seen or heard of it
> happening but have learned not to put much weight in my own narrow
> anecdotal experience. If Fraysee is anywhere close to correct there
> should be hundreds or more probably thousands of such tales out there
> to be related by list members.
>
> How about a show of hands?
>
> Kurt Sperry
> Bellingham, Washington
> USA
>
> On Fri, Feb 18, 2011 at 8:36 AM, Charles Andrews <chasds@mindspring.com> wrote:
>> Mike F wrote:
>>
>> Forty year old professional bikes, built with thin seamless tubing, that
>> have the original factory paint jobs, 90% of the time are not safe to ride
>> as they decay from the inside, just like termites that eat out and stop when
>> they reach the paint, the beam looks ok but the building falls down.
>>
>> I have to say, I wondered about that. Apart from anything else, re-painting a frame will not do anything to prevent rust from the inside out. Preventing that requires other measures.
>>
>> So I was struck by the logical disconnect.
>>
>> Charles Andrews
>> Los Angeles