New-York tribune., 1907-06-24
STRUCTURAL STEEL DEFECTS.
Editor Of The Tribune.

To the Editor Of The Tribune
Sir. VIII YOU permit me to use your columns in
continuing the discussion OF structural steel de-
fects as there seems TO have been some misunder-
standing of my letter which appeared in your
issue of the 18th?
II was not intended Ito convey that 1t the
custom to paint steel rails The particular matter
in mind structural steel. and the statement OF
George Simpson, chler engineer or the IhompSoh-
Starrett Company that 1T Is becoming more and
more the practice of builders 10 tnCase all OF their
steel In cement brings up another important feat
of tho situation.
To begin with. Of the ideas OF coating steel
with a transparent coating was specifically set
forhthat It permitted the detection of corroston
which may have already set in, and in that way
! the coating could be removed, II necessary, and
the steel properly cleaned before the hnal coatngs
applied. II the steel was found In hrst class
condition. the final coangs could be applied over
the bottoming coat. and this bottominS coat should
be an insulating material
A A Knudson at the 2l4th meeting of the Ameri-
can Institute OF Electrical Engineers, in March,
1907. presented interesting paper explaining the
disiutegration Of and concrete due TO cleo
trolytic action Tests were made at the electrical
testing laboratories in New York and showed that
metal incased in this manner and subjected TO
moisture and electric currents was rapidly eaten
by electric action and the concrete cement itself
disintegrated 1t IS we'll known that the stray cleo
trical currents leakages are present in all large
cities and IL has been pointed out before by author
ities on the subject that all OF our large steel
structures were subject TO the action OF these
rents even when the foundations were well In
sulated
In Knudson's experiments pipes were incased in
/
both fresh and salt water. They were connected
with OIL a1npere continuously flowing through them.
He reported a gradual disruption Of the concrete
as time on and the appearance OF electrolysis
and losing in weight of the tubes. The disintegra-
| ton Of the concrete a genuine surprise and
wherever blocks had been subject to electrolyss
their interior showed strong evidences OF electro
lytic action. A deposit of rust extended from the
pipe toward the outside CT the block along certain
! lines which acted like lines of cleavage. The
cement was found to be solid. that II could be
cut or scraped with knife. This solidity was
such that the point of a blade OF pocket knife
could be inserted In 1t far enough that the knife
was supported in upright position.
| He Furthermore states that in no sense can con-
crete be considered nsulatOr. and to all appear
| ances is just good elecuolyte as any OF the
! soils found the earth.
] NJ p. Wood. in his work on rustless coattngs.
states that lit is a false realization that masonry,
concrete or cement Is impervious TO moisture and
| incapable Of acting electrolyte such as would
induce electroyss. In closing he states that IT Is
not at all surprising that such currents appear on
steel work of bridges. whether incased in concrete
or masonry as these materials are no protection
/ from stray railway currents when the conditions
| are favorable for electrolytic action.
| | am unable to agree with Mr.. Simpson IN his
statement that "a slight initial coating OF rust Il