33
OF ENGINEERING FORMULAE.
Corrosion of Iron and Steel. (B. H. Thwaite.)
C — Coefficient of corrosion during 1 year’s exposure in lbs.
avoirdupois per square foot. (For value of C, seo
Table.)
W = Weight in lbs. of 1 foot length of the section exposed.
L — Length in feet of the perimeter exposed. If both the
inside and outside perimeters are exposed to the cor-
rosive action, they must both be Included.
W
* Y — The number of years’ life of the metal = -r—- •
C Lt
Table of Values of C.
Corroding Agents.
p .Ä
§ .
48
£
i
I
'S I
Cast iron.............
Wrought iron.........
Steel .................
Cast iron (skin removed)
by planing) .. .. f
Cast - iron surface pro- )
tected by galvanizing !
Cant iron In contact with brass
lbs. 1
*0656
•19561
•1944'
•2301
•0895
I
5
its.
0635
1285
0970
0888
PR
lbs.
•0381
•1440
•1133
•0728
0359
■03T1
„ „ copper.. .. ..
„ „ gun-metal .. ..
Best wrought iron in contact with brass ..
„ „ copper ..
„ „ „ gun-metal
els
lbs. I lbs. I
•0113!-0476j
•0123
■0125
■0109
•12541
•1252
•0884
0048 -0199
aS
lbs.
•1908
•2003
•3493
•2779
•4012
•4537
£
If painted once a year, multiply the result by 2 • 0.
„ „ in 2 years, „ „ 1-8.
» >, 3 „ „ „ 1’6.
* Y is baaed on the assumption that the metal is tolerably uniform in
thickness, otherwise the thin portions will have a shorter life than the
average of the section.
In experiments of iron in acid, it was found that the metals, according
to their impurities, lost most in the same time—steel less) than iron, soft
steel less than hard steel. Ou the second day tha soft steel lost more than
hard; on the fourth day the less was equal.