It apears the surface rust is covered.
This came straight from the Sprinter owner's manual.
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B. What's Covered

This warranty covers the cost of all parts and labor

needed to repair or replace any sheet metal panels

that get holes from rust or other corrosion. If a hole

occurs because of something other than corrosion,

this warranty does not apply. Cosmetic or surface

corrosion - resulting, for example, from stone

chips or scratches in the paint - is not covered.

For more details on what isn't covered by this

warranty, see 3.6.

This warranty has two time-and-mileage limits:

. For sheet metal panels, the limit is 36 months,

with no mileage limit.

. For an outer-body sheet metal panel - one

that is finish-painted and that someone can

see when walking around the vehicle - the

limits are 5 years or 100,000 miles on the

odometer, whichever occurs first.

3.6 Certain Kinds of Corrosion Not

Covered

Your warranties don't cover the following:

. corrosion caused by accident, damage, abuse,

or vehicle alteration;

. surface corrosion caused by such things as

industrial fallout, sand, salt, hail, and stones;

. corrosion caused by the extensive or abnormal

transport of caustic materials like chemicals,

acids, and fertilizers; and

. corrosion of special bodies, body conversions,

or equipment not made or supplied by

DaimlerChrysler Corporation or DaimlerChrysler.