Steels_ Metallurgy and Applications, Third Edition

Stainless steels 321

2.5 -

2.0 --

O
1.5-
8
11.

1.0-

0.5

t~

O

T"

409

0m z

L_

0

g

304

~ o,i

z

0

z

o

o

O3 0,,=,

z

(^143) r
~
z
L
r~
316 2205 .... 310

• 2.5

" 2.0

1.5

• 1.0

0.5

Figure 4.14 Prices of stainless steel strip relative to a value of 1.O for Type 304 at March

1997

Based on the prices quoted in the 2nd edition of this book (1994), Type 304

stainless steel strip was about 3 
89 times that of cold-reduced, uncoated, mild steel

strip. The prices of some high-alloy stainless steels, relative to Type 316L, are

shown in Table 4.9 (see p. 332).

Corrosion resistance

Stainless steels owe their corrosion resistance to the formation of the so-called
passive film. This consists of a layer, only 20-30 ,~, thick, of hydrated chromium
oxide (Cr203), which is extremely adherent and resistant to chemical attack.
If the passive film is damaged by abrasion or scratching, a healing process or
repassivation occurs almost immediately. In general, the corrosion and oxidation