, 1877-03-23
IIsON-I,UST.
4 London Chemist Announ'es Ms DivsrtfI sf 4
Certain Heans of Presenting II.
Tho Experiments Already Made Justify
Faith In the Method.
Description Of The New Process.

EonAn4 Tfrn*1, Hareh o.
A very important paper has lately been read
before tho Society Of Arts ly Mr.. Darf, Pro-
fessor OF Chc1ntstry to Tho Royal Academy,
upon a method Of preserving Iron from rtst BY
coating II with Us own magnetic oxide The
facts which Prof. Bar1 has brought for
ward, sud The specimens which he has exhibited.
arc such "A to Justify the belief that Ills dscov.
cry wilt prove to be one Of enormous value,
and that IL will, indeed, render all kinds Of lron-
work, however much cxposcd 70 weather or to
corrosive vapors Of liquids, practically tndc-
structtblc and everlasting.
When arl Iron surface Is cxposcd 10 tho action
Of wafer, ar Of moist air, II speedily becomes
cevctcu l,y 0!m VI proto1Idc, Or ferrous 61ilc,
whtrl, consists of to parts by weight Of tho
metal to 10 parts Of oxygen. TIC fcrrous oxide
continues 10 attract oxygen from tic atmos-
pllctc, and Is grad ualfy converted into auotl,cr
compound, tho scaqutoxtdc, or fcsric oxide,
Which Is composed Of twice 10 parts by weIght
u lrou, and three times 10 parts by weight. Of
oxyecn. The ferric oxide, In ita turn, Eivcs up
sosnc of It's oxygen to The as yet unoxtdlzrd
Iron beneath It. and the ferrous oxide thus
formcd Is gradually converted into fcrric
oxide by the access OF ntr through the
spongy laycr ui superficial rust which covcrs
II. In this way the frat formed film Of
rust exposes tU tl,e atmosphere the surface
wllicg, ics Gel0w It and hence the rust becomes
carrier of oxygen to tho deeper parts of the
iron, until tho latter Is completely eorrode1 and
worn through. Many attempts have been tradc
tn protect Iron surfaces by the application OF
Some kind Of paint or varnlsh; and these at.
tclnpts have, Of cuurse, hcan to some pnrtthY
extent successful. Sucll coattDgs, however,
have no real adhesion to tho metal on which
thov arc placed, aud are liable to scalc of or To
perish In q variety Of ways. Even when the
coating Is generally sound. the smallest Aaw 10
its continuity Will give entrance to the enemy;
for The rust from the exposed spot viii Spread
laterally under tho coating, snd may bc all tho
more dangerous aud destructive from being par
TALLY concrnlrd frou view.
It Is manifest that the evils incidental To rust
Ing arc entirely duo 10 tho unstable character
Of tile two oxides already mentioned, which aro
fortnctl spontaneously under ordinary Climatic
conditions. There II, however,, n third oxide
which possesses characteristics OF totally tiif-
by Inolst air, hut oven by ael1s and other corro-
sive substances. Ths Is tho magnetic " black
oxiIc Whit. conttsts OF three tlu1cs flty.stx
parts by weight Of tFon, and four times sixteen
covered that II any Iron article Is exposed, ut q
high temperature, IL the action. Of snptrhealai
stap., tt Jill become co,erfd ~ film Of tu blark
o1iatt, Of thfek1tsa sahteh u d1er,sfaeti by The
po,ure. Ths o1lic is har1er' tl,an tlat original
Iron, anl n'lhercx 10 Il eyeu more firmly than
the particles of irun adhere To each otfer. 10
that there Is 9nin not only III chymfcal, hut
aso T. en;t Il s osgHtE
llelt. and tic exposure Is continued for only
tlvc hours, asurfacc Is obtained Which will resist
enery-papcr far o Con*tderablc time. md which
win not rust within doors, or alter my moderate
process is conducted at ,oG0 degrees Fallrcnhcli,
and continued fpr sx Of seven hours, the sur
iacc will resist rasp. and Will bcar'any amount
81 exposure to weather. The oxidation docs not
why ttan b, turning Il black. 4 rough iuFrny
retains IT. rougllncst, and turned or polished
surfarc ruta.nb lis sinoothhess. II tAssp should
be any flaw In the coating, Or II the hauk oxldu
Is tiusignetlly removed frofl part of the surface,
H. thus left unprotected. Hut such oxidation is
strictly limited to tho unprotected portion, and
ua .l1t the htnai lcst tendency either to apEnhd
}aternsty under t'is black oxide or to dctae th!s
Prof. Dnrtf has as yet been limited In hts opcr.
attuns by the Wunt VI heating cl,ambar l1rru
enough to treat iron articles OF conhderabio
size, hut he has prepared n Erent number nt
Subjected to tests oi every kind. Such things
aa bolta, rlYets, screws, tloor-han,les glln'bar-
rcls, watcr-pipcs, ra1lng.hcads, cast-iron saucc.
VANS, aud oihur articles too ssumcsaus 70 ,nes,-
uon, have Gec, lcft for six wcuks of tlo recent
wet weather upon lawn at Dayswatcr, an.l nt
Tie expiration Of tat time wrru taken IN af,sn-
jutely unchanged, and without spock nf rust
sxevpt upun rurts WHICH we're left, either by
design or acetdrnt, without protcrtto,,. Ono ot
the epcctnc1ls shown by the SocIcty Of Arts wns
| 4 ln,E bolt, ir0m hall the length al which
! Vrni. barH lad e,t away tho cna.ins of black
oxl,lu t,cfore leaving tho bolt upon the lawn
| Tho se,upcd purtton WIS covcrcd With conslu.
crusnle IclsIlrsh OF srsquoxId0, but the eoatatl
rnrt lad icl,laf1lcd unchanged, nt,l IL was In.
f1ssfhlo Ia raise the tltn NJ black oxide at tht
| Ilnu UI dcn,areaton. Tho film wa. an integral
part nf thu Iron Itself, und tl'u Que coll not Nt
| detached tron, thu other. Another specimen
was tho head Of ntpc for collecting rpoi-wAAcr,
| which had been broken by a Ale4lsr.hatNtntr
nItcr It was coatct, a.Ml tlur thrown lto eIult
| IN rrof. Bnrfr's laM,ratory, where not onl,
stun!ty pa.saR over T.. ltast had formed q .,
lne A7AetuIeu eutes, u!e l'ie p1o1ectca ba''"eca
|