newbie question - electrolysis

Hard to say, but I'd suspect a systemic problem since the aluminum skin is all electrically connected. You can think about this as an unwanted battery, the aluminum is one terminal of the battery and probably some steel members are the other terminal. The white powder you see is corroded aluminum. The blisters form because that white corrosion is pushing out the weakened skin in that spot. You'd have to take off skin panels until you saw no more signs of corrosion. And you'd have to find out why it is occurring in the first place and stop it before you replaced the panels. You may be talking about thousands in damage.

I spent my work life dealing with this sort of thing, we spent hundreds of thousands a year in trying to prevent it in an industrial setting.

Do not buy that trailer is my advice, listen to what people are telling you.

BK

thank you all for your responses.
i shall proceed accordingly or at the very least with extreme caution with your recommendations.

so the general thoughts are this is a systematic problem and not just an isolated panel?

photos can be seen at the following:
front panel

Let me try to explain Electrolysis in laymans terms...Basically what is happening is a chemical reaction between two differents types of metal and the "bumps' that you are seeing is just the beginning of a serious problem that will contaminate , rather it has already, the entire area and the only solution is Removal of affected area and Replacement of contaminated metals.
JMHO hope this helps

Hi,

Run, don't walk, away.

What you are seeing is electrolytic corrosion. You are probably seeing a tiny portion of what lies under the paint. Don't buy it, Steve is right.

how so?
what is the rest of the iceberg?

Yes you should be worried about these bumps. I would strongly suggest finding
another rig to buy!
The bumps you see are only the tip of the iceberg
Steve