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Патент USA US3041225

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United States Patent Office
3,041,215
Patented June 26, 1962
1
2
coatings of the present invention, the following are pre
3,041,215
ferred: succinic acid; rnaleic acid; salicylic acid; tartaric
acid; phthalic acid; acetic acid; benzoic acid; and citric
SOLUTIUNS AND METHODS FOR FORMING
PROTECTIVE COATINGS 0N TITANIUM
Herbert Arthur Henry Jenkins and Dennis Br'nn Free
rmn, Brentford, England,
to Parker Rm:
Proof Company, Detroit, Mich., a'
of Mich
acid.
Acording to a feature of the invention, advantages are
realized when solid materials are used as the source of one
ign
or more of the above group of acids and/or the other in
No Drawing. I'îled Feb. 7, 1956, Ser. No. 563,865
gredients of the solutions. The solid compositions are
priority, application Great Britain Feb. 7, 1955
much less corrosive than the solutions so that packaging
1 Ch'lns. (CL 14S-6.14)
10 and handling are facilitated, and economies in storage and
transportation are effected.
The coatings of the invention are formed by contacting
the surface of titanium and the like with an aqueous solu
tion containing one or more of the adds of the above
This invention relates to the formation of adherent pro
tective coatings on titanium and more particularly to
chemically formed fluoride coatings on titanium and
titaninmbasealloys.
group, viz., hydroñuon’c acid. and hydrochloric acid,
It is an important object of the invention to provide
nitric acid or sulphur-ic acid and an organic acid having a
primary dissociation constant less than 3 X 10-2 but greater
strongly adherent coatings on surfaces of titanium and
than lxlO‘" at a pH between 2 and 6; the solution also
titaniuxnbasealloys.
containing at least 0.5% iluoride ions and at least 0.5%
Otherimportant objects oftheinventionaretoprovide
arüclesoftitaniumandoftitaninmalloyswhichhave 20 sodium or potassium ions or both. Preferably the con
centration of the above group of acids is maintained so
iormedthexeoncharacteristiccorrosionresistantcoatings
improved solutions and methods for chemically forming
andtoprovidesaidarticlesinsuchcoatcdformwhereby
dieymaybedeformedandooldworkodwithoutiniuryto
that the pH of the solution is vn‘thin the optimum range of
2.5 to 5. The anion radical of these acids which disoci
ates imm the hydrogen radical appears to be the most
important factor accounting for the similarity in elîect on
coating of thœe acids when present in the solution, and
tbesubsuate.
'l‘heaboveandotberobìectsoftheinventionwillbe
description.
Inacoordancewiththeìnventimtitanirnnandtitanium
basealloyscanbemnvidedwithauniformadherem
come apparent during the course of the following
consequently while
including other acids may
be present in minor amounts, it is imperative that the
greater part, and preferably all of the acidity of the solu
ñuoridecoating which facilitates drawingandoold work¢ 30 tion is derived from one or more of the acids of the above
ingofmemetalandwhichimpartsdaeretosuperiorcor
rosionresìstance. Forrna?onofthecoatingoccursfrom
asurfaeeofthemetalwithanaqueousacidic
solntioncontainingtbellnorideionandionsofoneor
moreofthealkalimetals. Forpurposesofthepresent
inventiomammonîumisinclndedinthetermalkalimetals.
tainedforthesolutionandpreferablythepliismain
group.
It has been found that the coatings obtained with solu
tions containing sodium are formed more rapidly than
those obtained with solutions containing potassium. If
35 ammonium or lithium ions or both are used in place of
sodium or potassium, their concentration must be substan
ItisessentialthmapHbetweenaboutZandóbemain
tiallyincreased. and,intbe caseofammonium,thecon-
taincdbetweenabout25and5.
InthecaseoflithiumitispreferabletonseatleastZ‘ió
Ithasnowheenfonndthatacertaingroupofcom
centratíon ofthe ammonium ion should be at least 2%.
40 but it is possible to use less.
Unless otherwise'. indicated.
ponndshaveìnthennusualelîectofreactingwith
percentagesasgiventhroughouttheareby
andtheiomofthealkalimetalstoforman
beusedandinthisœsetheminimnmconcentratlonwil'llre
somewhere between the minimum
given
weight percent. Mixtures of the above alkali
títanirnnandtitaninmbœealloysinthepresenceofthe
ysnperìorandfromwhatappeaœatypeof
oftheooatingremainsunknowmbutitisknownfromits
propertiesandeñ‘ectstoheyadherentandpro
teotiveandtobeofsolntions havingthe
mentionedandoneoftheofthis
eertaingroup. Thedistimadvamagesof-theinvention
arerealìzedarlyunderthe
"
i
thatthe
partandpreferablyallotftheaa'dityofthesohrtionis
thrived fran one of this certain group ofoompounds.
Ammtheinvœtiomth'ßcertaingmupof
arealladdsandallexhibìttoamarkeddegme
Iethedescribedbeneficialpropertywhcnllst’ßdilllhßîYPe
œtheprinápalsouroeofaddity.
'Diegmpofaddssofom?toexhibítthispropertycom
prisesformhydrotluo?cacidwhìchhasitsowndistinct
ßwinappeanandarsohydxœhkaìcacìd.
45
may
above for the iom separately dependrng‘ on the relative pro
portions of each in the mixture. Excellent coatings have
been formed from concentrations of 8% alkali metal_ `non.
Thc Solution preferably should be
y free
from calcium andotherionsknown toformñnondesthat
are insoluble in aqueous solutions'
theñuorideionoccursby
allowingtlrerntoheprecxpr-v
as othervme'
tated as simple insoluble ñuorides. However,
:om
canbetoleratedintheamonntsusual'lyfmmdmtap
water, and comequently this water may be med for pre
paring the solutions. Using the solutiom with the above
groupofacidspresentinthestrengthsthe
concenu'ationofthelluorideionmustbeatleast0.9%
andcanbeœedinquantitiesbelowandabovesatura
tionwhichisappmximatelyoftheorderofl0% thoride
ion. 'I‘heprefcrredrangeofoonoentra?onoitheßuoride
ionhasbeenfoundtobebetweenaboutOß‘ië to8%.
andsimilarlytheirœehassepamteadvantages. Discov
Articlesrnaybetreatedeitherbysprayingorbyim
eredtobeequivalanoftheinm'
mersion and in handling of the solutions rubber or poly
ganìcadds‘intheireëectonhmalsohavingsepa
thœc-lined containers are
raœareorganicaa'dswhichhaveaprimary
‘
' '
umstantlœs than 3x10" butgreater than
1x10-ì Bygìmaryconstantismeantthe
'
'
s
:~-
at approximately mom
‘"‘wmore
mlhmthereare
oneatnms. -Ofthelatter
adds,i.e.,theorganicacidsewhichareuse?rlfnrforming
as the solunom‘
are corrosive.
Entirely satisfactory coatings can be formed without
any activation or chemical
of the
surfaoett- However, it is oftentimes
tirs!
to pickle the :nume with a solution
hydro~
A 5% hydmduorieacidsolntitm
hasbeenfoundtobeamefulpickle. Insomecasesthe
3,041,215
3
nature of the pickle solution may be a factor in obtaining
the most successful coating and in such cases its nature
must be determined by the particular titanium alloy to be
processed. Any grease that may be present on the sur
face as received for coating will generally be removed by
4
nitric and sulphuric acid, the solution can be prepared
from three ingredients, viz., one of these acids, a fluoride
and an alkali metal.
Alternatively, one of these acids
and an alkali metal ñuoride only need be used to supply
the solution. Advantageously, a solid composition can
this picltling, but if necessary, a preliminary degreasing
be used as the source of these acids and this feature will
treatment may also be applied. lf the titanium has been
be illustrated with respect to sulphuric acid. In the case
annealed it may carry a heavy scale, and this, of course,
of sulphuric acid, a bisulphate or sulphamic acid can be
should be removed also.
used as the source of sulphuric acid in the solution. As
From the evidence that is available, the coating action 10 these are solids, their use has advantages and an example
of these solutions appears to be the result of the formaof such a composition comprises a. solid mixture of a
tion of a thin layer of solution saturated with titanium
solid bisulphate or sulphamic acid, a solid ñuoride and a
at the surface thereof under treatment. Accordingly,
solid alkali metal compound. This will provide a work;A
when a fresh solution is brought into contact with the
ing solution when dissolved in water or an aqueous solu
metal surface there is a time lag before coating starts 15 tion. An even simpler solid mixture comprises two com
while the titanium metal is being dissolved from the sur
pounds, e.g., a bisulphate and an alkali metal ñuoride.
face. It is therefore preferred to add titanium to the
Good results were obtained from a solution prepared from
solution. It has been found that this can be accomplished
a mixture which comprises 5 parts by weight of solid
conveniently by adding to the solution just prior to im
sodium bisulphate and 4 parts by weight of solid sodium
mersion of the metal enough ñuotitanate compound to 20 fluoride which is dissolved in water in the quantity of 9
saturate the solution and simple tests under operating con
parts by weight of the mixture to make 100 parts by
ditions can be made to determine the amount required
weight of solution.
in a particular operation. A tluotitanate compound such
In the case of the organic acids which have a dissocia
as an alkali lluotitanate, as for example, potassium ñuoti
tion constant between lXl0-‘ and 3Xl0-3, the solutions
tanate can also be included in the coating solution initial
tobebroughtîntoeontaetwiththemetalsnrfacecanbe
ly and it can be mixed with the solid compositions preprepared by dissolving in water three ingredients, name
viously mentioned for making up the solutions.
ly, the organic acid, a compound yielding fluoride ions
The solutions can be prepared by dissolving three in«
and an alkali metal compound. If desired, two in
gredients in water, viz., one of the above group of acids,
gredìents can be used, namely, the acid and an alkali
atìuon'deandanalkalimetalcompoundandinthecase
30 metal tluoride. Ether a solution ready for use or a con
of hydrotìuoric acid, two ingredients, viz., the acid and
centrate whichisdilutediustpriortousecanbepre
an alkali metal compound. Alternatively, in the case of
pared. As some of the organic acids, e.g., citric and
the other acids, two ingredients can also be used, viz.,
tartar-ic acids, are solids their use in such form provides
theacidandanalkalimetalñuoride.
the advantages previously set forth for the solid ma
With respect to the above group of acids, while they 35 terials. A solid composition according to this feature
an: substantially equivalent in their eñ'ect on the type of
of the invention comprises a mixture of a solid organic
coatingformedeachorcertainoftheacidsofthegroup acid having a primary dissociation constant between‘
have specific advantages when used in the solution alone
1x10-4 and 3x10-z with a solidofone ormore ofthe
andthispropertyofcertainoftheacidsmakesnatural
subgroupiugs from the above group of acids. The use
of hydroñuon'c acid without the others oi the group
compounds providing the fluoride ion and the alkali metal
ion when dissolved. Even greater simplification of the
processarisesfromtheuseofasolidmixturewhichcon
intbesolutionasthepredominantorsolesourceofthe
sists of only two compounds, as for example, citric acid
acidity thereof has the additional advantage that the com
plex ñuoride coating formed does not contain any other
acidorsaltthereofenuainedorotherwisecarried over
and sodium or potassium ñuoride.
from the solution. The main advantage (in addition, of
The following examples illustrate the improved acid
fluoride coating solutions of the present invention and
method of applying these solutiom to surfaces of titanium1
course,tothosedesc?bedfortixegroupasawhole) in
andaregivenwithrespecttoeachoftheabovesub`
using alone the other mineral acids, namely, hydrochloric,
groups of acids, namely, hydroiluoric acid, and the ruin~
eral acids, hydrochloric, nitric and sulphuric acid, and
the organic acids.
Example I
niu'icandsulphmicacid,isthattheyarecheapand
readilyavailable. 'I‘headvantageoftheuseoftheor
ganicaddshavingadiœociationconstantassetforth
above without the others as the sole source of the
acidityofthesolntionisthattheeonn'olrequiredtomain
tainthepHwithintherequiredrangeissìmpler.
Hereinafter,theìnv¢ntionwillbedescn`bed withre~
spccttoeachoftheabovembgroupsoftheacidsofthe
generalgroup. ln tbecaseofhydrotìuorkacíd, the solu
tionœnbeprtparedbydiœdvinginwatertheaddand
an alkali metal compound. Altcmativdy, a Solution of
an alkali metal bìñnoride can be used to provide the es-
sentia! constituents of this solution. In accordance with
the feature of the invention wherein solid materials are
employed to facilitate storage and transportation, a solid
composition can be made by mixing a solid bißnon’de
and a solid compound o( an alkali metal which when dis
solv'edìnwates-,ormanaqieoussolntiomwillprovidea
woúing solution. If the cation of the solid biñuoride is
analkalimetahaánglesoiidcompotmdcanbemedfor
dzissolurionwhichmakœtheprocessextremelysimple
andconvenient. Forcxample,a 15% solution made
frumwlidpotassinmbiñuorideanda 12% solutionmade
from solid sodium biñuoride each produced a strongiy
adhauzt brown-gray coating on titanium.
lnthemeoftheotherminaaladdshydrochloric,
Coatings were produced on titanium by the various
hydrotluoric acid or hydmiluoric acid~pr0ducing solutions
set forth below by pickling titanium panels for 30 sec
onds in a solution of nitric acid and hydroñuoric acid,
rinsingthemandthenimmcrsingthaninthevarîrms
solutionsatroomtemperanneuntilgassingstopped. The
solutionsandthecoatingweightsohtainedwere:
3,041,215
5
6
Example 2
Example 8
The solution consisted of:
The solution consisted of:
Percent
H2904
Perœnt
1.5
'KF
Acetic acid 48
Potassium ñuoride ........................... _- 6
5
NaNO,
XiTiP.
0.25
0.1
Water to make 100%.
Darkmyooatingsofgoodadhœionwereformedon
Water t0 make 100%.
Ahavinggoodadhesionanddarkgmyinap
titaniuxninSminutesatZD‘ C.
Example 3
The sohxtion eom'sted of:
in which the various objects hereinabove set forth, to
gether with many thoroughly practical advantages are
ltwìllthusbeseenthatthcrehasbeenprovided by
'pearanoewaspmduœdinßómimnesatZO’C
invention, an article, a composition and axmethod
successfullyachieved.
0.25
0.1
Sinœcatainchangesmaybemadeintheaboveinven
madewithoutdepartingfromthescopeîhcreoßìtisin
tendedthatallmattercontainedintheabove-describeddis
closureshallbeintexpretedasilbßtrativeandnotina
Thesamepmducxwaansedœindnahoœuampte
Whatisdaimedis:
l. Anaqueoœacidicsolution for pmducingaooating
Percent
KHSO.
7
KF
tion and different embodiments of the invention may be
5
NaNO,
KJEF.
Watcrto make 100%.
.andtheaamensuhsweœobœinei
onsurfacœoftitaniumandlitaniumbaaealloyshavinga
pHbetweenZandóandgofatleastabontOßïó
oftheñuorid¢ion,atlœstabont0.5%ofthei0nsof
atleastoneoftheaikalimetalgandanacidselected'ù'om
Example4
The solutionof:
the group
5
of hydroñuoxic acid, hydrod?oxic
acid,nít?cacid,amisulphuxicacid,thcoonoenn~ationof
saidacidhnthesolutionbdngsuchthatthe
30 panoftheacidityofthevsolutionisderivedtmmsaidadd.
LAnaqueousacidicsolutìonforproducingawating
onsurfaœsoftitaniumandtitaniumbasealloys‘havinga
pHbetween2and6andofatleastabout0.5%
35
oftheñlwrìdematkastaboutûßîôoftheíonsofat
leastoneofthealkalimetals,andanacidselectedfmm
the group
of hydmñuorie acid, hydrochloric
adinit?cadiandsulphn?caciiñlcœncmtrationof
saidaeidhtthesolutionbcingsurhthattbe.
partoftheacidityofthesolmionisdctivedfmmsaid
acid.
3. An
for-producing aooatíng
onsurfaœsoftitaniumandbmealloyshavinga
pHbdWCellZvand 63nd HHC'HH; d3b0lü0.9% @8%
Watertomake im.
ßno?deiomat-leastabomlß‘ñionsofatlestoneof
45
ofsaidaádinthewhläonbdngsnchthattheprt
panzoitheacidítyofdtesohxtion'ßde?ved?'ommid
acid.
4. An laqueous addì: solution for
'lbsurfaœofthewirerennìnedmgoodoonditíonrhlr
'
50
îtlgthedmwmg
mik
Wata'tomkelm.
beíngsuch that thepne
'
amd
Pemem
7
lo
6_Anaqneousaddicsolutionforaoœting
onsmiaœsoftitaninmandtitaníumbasealloyshzvmga
pHbetwoen2and6andofabout0.9%to8%
horideiomatleastabontíij'ißionsofatleastoneof
Erample7
Theaolutiond:
Imi-ile
partoftheacitñtyofthesoluñonisdexivedfmmsaid
and.
7.Asolidoomposítionsolublemwamsoastoform
asolutioncapableofanadheœmon
surfaœsoftitanimnandhaseaßoya
Puvmt
5
l0
Wmertomakelm.
DarkafllereatwerefœmedoninS
ninnesltZO’C.
partoftheacidityofthesolutíonisde?vedfmm
acid.
$.Anaqueousacidicsolutionforpmducingaooating
onsnrfaœsoftítanimnandtitanimnmealloyshavùlga
p}{betwen2and6andofabout0.9%to8%
ñuorideiomatleœtaboutoj‘îôkvœofatleastoneofthe
ofsaid
addinthesohltionbeingsuchthatthepan
ofdxeacidityofthesdutionìsderivedfmmsaidadd.
Daxkadhexmwueñornndontitaninminí
n20‘C.
PlmnlicacìL“
pHbetwem2and6andofabout0396to896
mxxidematleastabout0596ioœofatleastoneof
mmelnmusetfonhnhove.
Exampká
Theaoluánnof:
Gil't?d
-actuating
onsurfaoesoftítaniumandtitanium base alloyshavìnga
75
oflanúxuneofabiñnorìdganalkalimaal
andainanamomnsutñcíanto
3,041,216
8
consistingoiabout0.9%to8% oftheñuorideiomat
saturate said solution, the proportions of said biñuoride,
alkali metal compound and ñuotitanate being such as to
produce an aqueous acidic solution having a pH between
2 and 6 and containing at least 0.5% of the ñuoride ion
oftheacidityofthesolutionisderîvedùomsaidadd.
andatleast0.5`% of theaikalimetalion.
13. Amethod for producínganadherent coatingon
8. A solid composition soluble in water so as to form
the surfaces of titaniumandtitaniumbasealloys com
a solution capable of producing an adherent coating on
surfaces of titanium and titanium base alloys consisting
ofamixtureofatleastoneoompoundofthegoupsul
phamicacidandabisulphatgañooridqandanalkali
metal
10
the proportions of said acid, fluoride,
andalkalimetalcompoundbeingsuchastoproducean
acidicsolutionhavingapHbetween2and6and
containìngatleast0.5% oftheiluorideionandatleast
0.5%ofthealkalimetalion.
9. Asolidcompositiousolubleinwatersoastoform
ousacidncsolutxonhavmgaplîbetween2and6and
cormstingofabout0.9%to8%oftheñnondeion,at
leastabout0.5% oftheiomofatleßtoneofthealkah
metalgandnitricadmtheconœntrationofsaidacidm
thesolutioubeingsnolxtliattlsetpartoftlzkr
addityofthesolutionisderìvedfromsaidacid.
15
i
14.Amethod for producinganadbermtcoating on
thesurfacesoftitaniumandtitaniumbasealloysoom-
prisingmbjectingsaidsnrfaoestotheactionofanaqw
a solution capable of producing an adherent coating on
snrfacesoftitaniumandtitaniumbasealloysoonsisting
ousaddicsolntionhavùigapHbetwecnZandóand
ofabout0.9%to8%oftheñuo?deion,at
meutiallyofamìxtureofatleastoneoompoundofthe
groupsnlpharnicacidandabisulphate,añuoride,analkali
metal compound, and añuoù'tanatein anamountsnñì»
cienttoaatnratesaidsolutiomthepxoportíonsofsaid
acid,ilnu|-ide, andalkalimetaloompoundbeingmchas
toproduœanaqoeousacìdicsolutìonhavíngaplibe
0.5%oftheionsofatleastoneoftbealkali
mlphnricadd,theofsaidacid
beingsuchthattheprcdaninantpartof
twem2md6andcontaix?ngatleast0.$% oftheñuoride
ionandatleast0„5%ofúxealkalimetalion.
10. Amethodfœprodncinganadherentcoatingontbe
surfacesoftitaniumandtitaniumbasealloyscomprisìng
saidsmfaœstotheaclionofanaqueomacidic
solutionhavingapHbaween2and6andconsistingof
atleastaboot0596oftheñuoridciomatleastabont059â
oftheionsofatleastoneofdiealkalimetalgandan
metakandanacidselectedfromthe group
aœ’d selected from thegxonpofhydroñuoric
tlnofsaidacidinthesolutionbeingsnch
thatthepartoftheacidityofthesolutionis
hydrcñmicadihydrochloricmnit?caciíand
md'
Ȣ,|~-|| :.lri
Sl tionbeingsndnthatthepartoftheacidity
lLAmet‘hodñormadha'entcoatii-igon
ñleslxfaœsofandh’œnimnbœealloyscom
pris'ngaaidmfaoœtntheaetionofanaque
oœ
apHbetween 2 and 6 and
Mecnœsœinthcñlcofthispatent
40
ofabout0„9%t08% oftheñun'ideioma:
leastaboutoßßoftheionsofatleastoneofthealkali
metals, andlrydroho?cmthe
ofsaid
acidinùeadutionbdngsuchthatthepart
oftbead?yoftlnisdœiwd?omsaidadd.
*lw
onsacidics'dutinnhmingaplîbetwemzandóand 50
UNITEDSTA’I‘ESPATEN'IS
2,489,152
2,550,660
2,71 1,364
2,864,732
Panepinto .... -....... Nov. 22, 1949
Amnndsen -....__....... May l, 1951
Beach ........._-..._._ lune 2l, 1955
Miller et al. ___-...__ Doc. 16, 1958
O'I'HHIREFERBÍCES
“ñnalReportœGlmSurfzœTreatmemofTnani
uninWatawwnAnmal‘byBattelleMemmiallmti‘
mOctoherSO, 1953,30pages.
Amlunell,l95l,p.l52.
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