Thanks for your patience. The metallurgist has confirmed my suspicions.  The steel is plated.
That is why the lab results differ from the XRF results.
We were interested in identifying the steel alloy the semi-cyindrical artifact is made of.  We have multiple XRF readings but we wondered if they might be "polluted" by contaminants on the surface of the artifact, so Rick Freeman took a small piece that had broken off the artifact and ground it down until he could see bare, shiny metal. In so doing, he inadvertently ground off the plating, so what the lab analyzed was the base steel minus the plating. What the XRF was seeing is the base metal, plus the plating, plus a layer of paint.

The base metal is carbon steel allied with a little manganese.
Based on averages of the XRF readings, the plating is:
Tin  4.587%
Zinc  1.407%
Manganese 0.458% (minus the manganese in the steel alloy)
Copper 0.394%
Cobalt 0.736%
Chromium  0.129%
Molybdenum 0.125%
Vanadium   0.125%

The paint is:
Silicon   2.633%
Titanium   1.398%
Lead 0.129%
and maybe some of the Cobalt.

"Tin cans" are steel plated with tin as a corrosion inhibitor. They've been around since 1840. The tin plating on this artifact is much more complex than a can of peaches, but its purpose is the same.  The paint added a further layer of protection.  Whether or not it is part of the PL8's water tank, somebody really didn't want this thing to get rusty.
Nevertheless, the portion of this object that was exposed to the pond water corroded completely away over the decades. 
What does that say about the survivability of other un-buried and mostly un-plated steel debris?  No wonder our visual searches have found nothing.

ho Ric, I'd be upset if you had problems with your payroll controller. So I will wait.

BTW i will receive soon a good and lengthy Monography regarding Lorraine Dietrich. You know that this manufacturer first designed sportcars ? Did it ever occur to you that this water tank might have been derived from car apparatus?

Night is coming in Dordogne and i have my little son to care of. I have to tell him the story of a strange big seabird that vanished across the Atlantic some 100 years ago. Take care, I will keep in touch.

As we say in French: 'je donne ma langue au chat'.

LOL! Sorry.  As we say in English, this is way above my pay-grade and I'm trying not to embarrass myself more than usual.

Well Ric, you've sparked my curiosity!

As we say in French: 'je donne ma langue au chat'.

In any case, this common low-alloy steel can undoubtedly be used to make tanks or containers not exposed to particular mechanical or thermal stresses.

From my casual eye, I'd say that only a few factors explain a transformation of the artifact:

- high heat; intense cold;
- exposure to the environment or to a persistent element in that environment;
- the passage of time leading to chemical transformations?

If I'm right, the answer is a lot simpler than that, but I don't want to shoot off my mouth until I have confirmation from the metallurgist.

I'm the one who was 'staggered' when I read today's newsletter.

If the EDS test is correct, and there's no reason to think otherwise, then, except for a measurement error, the previous XRF test would have been altered by some other agent(s) or factor(s).

Firstly, common 1010 steel, which is low-alloy and very soft carbon (class A or Adx ('mild steel') according to the 1920 Houille Blanche classification, would have only 0.30/to.60% manganese as a common element with the artifact. If we disregard traces of phosphorus and sulfur, which give an idea of the steel's purity, then yes, we have a very common steel.

This wouldn't be such bad news, since what I immediately found of the current French version of the '1010' (Arcelor/Mittal) gives us a composition similar to that of the 1920 Class A - 'Houille Blanche' type:

C: 0.08/0.013
Mn: 0.30/0.60
S: 0.035
P: 0.025

https://sections.arcelormittal.com/catalogue/B50/FR

The question of silicon remains. I can't explain the very high levels of this element.

From my casual eye, I'd say that only a few factors explain a transformation of the artifact:

- high heat; intense cold;
- exposure to the environment or to a persistent element in that environment;
- the passage of time leading to chemical transformations?

This steel was most probably in common use in France in the 1920s.

Among the types of use, La 'Houille Blanche' specifies that type A 'extra-soft' is used in particular for “cold-formed sheets and parts
hammered'. Apparently, this is also the case for welded parts.

you have been posting some VERY informative and interesting information from a different point of view and the input is appreciated.

I am seeking for more 1930's metallurgy studies about french spécial steels. l am planning to buy the latest monography about Lorraine-Dietrich manufacturer.

Last, i have the advantage to live not too far from Biscarrosse and the Musée de l'Hydraviation where a very similar E12b 450 cv is exposed. I will try to jump in there one of these days.

Also on that note and additional question is if a plane uses more fuel on one side of the plane than the other will the weight difference force the wings to either move left or right or angle off. Let me know...thanks

More weight on one side tends to make the plane tip toward that side.

Curious to know if she worked from side to side as a balance or worked from left...then right with her fuel usage. It will be interesting to find out from you Ric or Andrew Mckenna as to how this would work with all the changes and modifications it did to the tanks overtime. Let me know...thanks

Pilot's normally switch tanks periodically to keep the ship balanced. Some fuel systems are more complicated than others.  Earhart's was necessarily very complicated. I don't know exactly how she managed her fuel because I wasn't there.

No apology necessary- you have been posting some VERY informative and interesting information from a different point of view and the input is appreciated.

Both The White Bird, and Earharts disappearances are mysteries we would love to be able to solve!