<s>
Disc	B-Device
rot	I-Device
is	O
the	O
tendency	O
of	O
CD	O
,	O
DVD	O
,	O
or	O
other	O
optical	B-Device
discs	I-Device
to	O
become	O
unreadable	O
because	O
of	O
physical	O
or	O
chemical	O
deterioration	O
.	O
</s>
<s>
The	O
lacquer	O
protecting	O
the	O
edge	O
of	O
an	O
optical	B-Device
disc	I-Device
can	O
usually	O
be	O
seen	O
without	O
magnification	O
.	O
</s>
<s>
In	O
ordinary	O
use	O
,	O
a	O
surface	O
layer	O
of	O
aluminium	O
oxide	O
is	O
formed	O
quickly	O
when	O
an	O
aluminium	O
surface	O
is	O
exposed	O
to	O
the	O
atmosphere	O
;	O
it	O
serves	O
as	O
passivation	B-Application
for	O
the	O
bulk	O
aluminium	O
with	O
regard	O
to	O
many	O
,	O
but	O
not	O
all	O
,	O
contaminants	O
.	O
</s>
<s>
CD	O
reflective	O
layers	O
are	O
so	O
thin	O
that	O
this	O
passivation	B-Application
is	O
less	O
effective	O
.	O
</s>
<s>
Since	O
disc	B-Device
rot	I-Device
is	O
often	O
caused	O
by	O
the	O
corrosion	O
of	O
aluminum	O
,	O
this	O
means	O
that	O
DVDs	O
are	O
more	O
resistant	O
to	O
disc	B-Device
rot	I-Device
.	O
</s>
<s>
Each	O
type	O
of	O
optical	B-Device
disc	I-Device
thus	O
has	O
different	O
susceptibility	O
to	O
contamination	O
and	O
corrosion	O
of	O
its	O
reflecting	O
layer	O
;	O
furthermore	O
,	O
the	O
writable	O
and	O
re-writable	O
versions	O
of	O
each	O
optical	B-Device
disc	I-Device
type	O
are	O
somewhat	O
different	O
as	O
well	O
.	O
</s>
<s>
Because	O
they	O
are	O
less	O
expensive	O
,	O
the	O
industry	O
has	O
adopted	O
aluminium	O
reflecting	O
layers	O
as	O
the	O
standard	O
for	O
factory-pressed	O
optical	B-Device
discs	I-Device
.	O
</s>
<s>
Using	O
surface	O
error	O
scanning	O
to	O
check	O
the	O
data	O
integrity	O
allows	O
discovering	O
loss	B-General_Concept
of	I-General_Concept
data	I-General_Concept
integrity	I-General_Concept
before	O
uncorrectable	O
errors	O
occur	O
.	O
</s>
<s>
Many	O
HD-DVDs	B-Operating_System
,	O
especially	O
those	O
produced	O
by	O
Warner	O
Bros	O
.	O
between	O
2006	O
and	O
2008	O
developed	O
disc	B-Device
rot	I-Device
not	O
long	O
after	O
production	O
.	O
</s>
<s>
Disc	B-Device
rot	I-Device
was	O
also	O
more	O
common	O
on	O
double-sided	O
HD-DVDs	B-Operating_System
than	O
on	O
single-sided	O
HD-DVDs	B-Operating_System
.	O
</s>
