Note: Descriptions are shown in the official language in which they were submitted.
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~esc, i,~lLiGn
COMPOSITION AND PROCESS FOR SIMULTANEOUSLY CLEANING AND
CONVERSION COATING METAL SURFACES
Technical Field
This invention relates to a surface l,~:dL."ent ",etl,ocl that simultaneously
cleans and conversion coats metal surfaces and is app' ~ le to a variety of met-als. More specilically, this invention relates to a simultaneous cleaninglconver-
sion l,~dl-"ent method that is capable of simultaneously cleaning and conversioncoating a metal surface bearing oil, grease, etc., with the uniform formation
thereon of a fine and dense conversion codli- ,y.
Background Art
Zinc phosphate conversion treatments are currently in wide use as under-
paint coating treatments for the purpose of improving the post-painting corrosion
resistance and paint adherence of metals. This technology is effective even
when the metal suL,sl,ale is made of iron or is a composite that contains several
types of materials.
Zinc phosphate conversion coatings are typically formed on various met-
15 als, for example, by executing the following steps in the given sequence:
(1) alkaline degreasing
~2) water rinse
(3~ conversion l, eal"~ent
(4) water rinse
(5) drain and dry.
When this sequence is used to lay down an underpaint coating, a surface-condi-
tioning l,~l"~ent using a titanium colloid l~ ent composition (any liquid treat-ment composition alternatively being designated herein as a "bath" for brevity,
even though it may be used by spraying or the like rather than or in addition toimmersion) is run as a p,~ttedltoent to the conversion step ~3) for the purpose
of ultimately forming uniform, fine, and dense conversion coating crystals.
Surface conditioning with a titanium colloid treatment bath activates the
surface of the metal substrate and thereby induces the deposition of fine-sized
conversion coating crystals and ~Gc~lerdles the rate of conversion codling forma-
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tion. The disparily in the rates of conversion cGdlil ly fol IndliGn becomes particu-
larly significant at relatively lower treatment temperatures below 60 ~~.
One ~,ruble. ~, with the above-des~;- il~ed prior-art surface treatment technol-ogy is the large number of steps, which makes the overall process quite lengthy
5 and thus necessitates large-scale treatment facilities and large amounts of
space. Not only does the above-desc- ibed surface treatment technology consist
of five or six steps, but the alkaline degreasing and water rinse steps are fre-quently implemented as multi-step prucesses in order to improve the cleaning ef-ficiency This raises the facility costs even further and also reduces the produc-
.0 tivity by necessitating a substantial amount of time for the substrate to passthrough the entire lledllllel)l process.
A second problem with the above-described prior-art surface treatment
technology originates with the large number of factors that must be managed.
For example, the alkalinity (total alkalinity and free alkalinity) of the degreasing
15 solution must be mallaged in the - "~ali. ~e deyr~asil ~y step, while the acid concen-
tration (total acidity and free acidity) of the treatment bath must be n Idl layed in
the conversion l-edl-nent step. A major operating burden is imposed when the
factors that must be managed cover so broad a range. A large cost overhead
is also generated since reagents are consumed in each individual step. Moreov-
20 er, the main component in the surface-conditioning l,~dl"~enl agent is a titanium
colloid dispersion, which does not have an entirely satisfactory timewise stability
and as d result must be suitably managed and periodically discarded and re-
newed.
It could be conjectured that these two problems could be solved by run-
25 ning the steps from alkaline dey~easLIy through conversion treatment as a singleprocess through the use of a surfactant-containing zinc phosphal~:-based conver-
sion ll ~:dll "ent bath for the joint execution of degreasing and conversion. How-
ever, when the dLlt mpt is made to execute dey~easi~ ~9 and conversion simultan-eously, the conversion reactions begin sequentially from the regions of the metal
30 substrate that have been cleaned. This creates a pronounced tendency for the
quality and appearance of the resulting conversion coating to be nonuniform.
In another appruacl " the surface-conditioning agent could be added to the
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conversion Ir~dl" ,ent bath in a, lli~;~Jdliol, of ge,)er~liny a surface-conditioning ac-
tivity on the metal sub~l-dle during l-edl..,ent by the conversion treatment bath.
However. the titanium colloid main component is unstable in the acidic region
and a surface~onditioning activity therefrom absolutely cannot be expected. Ac-
cordingly, even when the surface-conditioning agent is used in conjunction with
the conversion lredl."e,~l bath, fine-size coating crystals are not produced andin fact, due to a slow rate of film deposition, the nonunirum,ily in conversion film
appearance ends up being even further emph~si~e-l.
Thus, as described above, there is fairly strong demand for a shortening
tO of the current llt:dlll)2nt sequence in order thereby to reduce facility costs, re-
duce reagent costs, and simplifytreatment bath Illanaye,,,enl. However, this de-mand remains unmet at present due to the substantial technical difficulties thatmust be surmounted in order to satisfy this demand.
Disclosure of the Invention
~5 Problçms to Be Solved by the Invention
The present invention was developed in order to solve the problems de-
scribed above for the prior art. This invention introduces a method for treatingmetal surfaces that sho, l~ns the zinc phosphate conversion treatment sequence
of alkaline degreasing - water rinse - (surface conditioning) - conversion treat-
20 ment - water rinse - drainldry by running the steps from alkaline degreasing to
conversion tl~dllllent as a single step, that is, as a joint degreasinglconversion.
In specific terms, the present invention introduces a method for simultaneously
cleaning and conversion coating the surfaces of various metals that--by
treatment of a particular oil-beari.,y metal surface with a single treatment bath in
2s a single step--is able to simultaneously clean the metal surface and form thereon a uniform, fine, and dense conversion coating.
Summary of the Invention
It has been found that the addition of a I ,er~lo~r~ unexamined organic ox-
idizing agent, namely, organoperoxide, to the conversion treatment bath made
30 possible cleaning of the metal surface and the deposition of uniform, fine, and
- dense coating crystals due to the ability of the surfactant to clean the metal sur-
face and the ability of the organoperoxide to accelerate the conversion coating
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for.,.alion ~ d~tiGllS.
In specific terms, then, the treatrnent method accor~ y to the present in-
vention for simultaneously cleaning and conversion c~dli"g metal surfaces is
characterized by the simultaneous execution of cleaning and conversion codlil ,9on a metal surface bearing oil, grease, etc., by contacting the said surface with
a zinc pl~os~,hat~-based cleaning and conversion ll~dllllel)l bath that comprises,
preferably consists essentially of, or more preferably consists of, water, zinc
ions, phosphate ions, surfactant, and organoperoxide. Such a bath constitutes
a composition according to the invention.
10 Detailed Desc,i~liol- ofthe Invention. Including P.~fer.ed Embodiments
The organoperoxide concenl-dlio,- in the druresaid conversion treatment
bath is pre~erably 50 to 1,500 parts per million by weight (herei. I~rler usually ab-
breviated as "ppm") and, independently, the surfactant conce~ dlioil is prt:r~rdb-
ly 0.5 to 5 grams per liter (hereina~ter usually abbreviated as "gJL").
.~ No particular ~ lions apply to the type, shape, or dimensiû\ ,s of metals
that may be l,~ate~3 by the method according to the present invention. For ex-
ample, the method accGrdil lg to the present invention can be applied to a variety
of iron and steel rlldlel ials, for example, steel sheet and ~ir~CirerOUS metal-plated
steel sheet, and to a variety of aluminum n ,dlel ials, for example, aluminum sheet
and aluminum alloys such as aluminum-magnesium alloys and aluminum-silicon
alloys. The method according to the ~resel,l invention is applied to metals
whose surface has picked up oil, grease, and the like. The nature of this adher-ing material is not critical, and it includes such oils and greases as rust-prevent-
ing oils, press oils, and the like. The adhering ~ "dle- ial may also contain admixed
2~ dust, iron powder, and other CG ntall lil lanl~. Nor is the amount of adhering mater-
ial a critical factor.
The zinc phos~,hdl~ cladni,)g/conversion treatment bath employed by the
method acco,diog to the present invention is essentially an acidic aqueous solu-tion that contains zinc ions, phosphate ions, surfactant, and organoperoxide.
3Q The zinc ions cc nce, Illdliul ~ in this cleaninglconversion treatment bath is general-
ly preferably from 0.5 to 5.0 g/L. An adequate cGdli--~ weight may not be ob-
tained when the zinc ions conce"l,dlio" is below 0.5 glL; this leads to a decline
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in the coveraye ratio by the resulting conversion cGdli"g on the metal surface
and therebyto an in~de~ t~ post-painting corrosion ,t:sijld"ce. Concentrations
in excess of 5.0 g/L can cause a coarsening o~ the coaLi.lg crystals and can
cause the resulting conversion film to be nonuniform, thereby producing in partic-
ular a decline in the post-painting paint film adherence.
The phosphate ions concenlrdliol) in the cleaning/conversion treatment
bath used by the Ill~lllod accordi~ to the present invention is preferably from
~.0 to 30.0 g/L. ~o"cer,l, d~ l IS below 5.0 g/L can make it difficult to form norrnal
conversion coatings, while concenll~liol-s in excess of 30.0 g/L do not provide
o any adcliliol ,al i,)~relnenl~ in activity and are therefore uneconomical. The phos-
phate ions can be generated by the addition of phosphoric acid or its aqueous
solutions to the conversion l,~:dl--)ent bath or by the dissolution of sodium phos-
phate, magnesium phos~cl ,dle, zinc phosphate, or the like in the conversion treat-
ment bath. The stoichiometric equivalent as phosphate ions of any of these
~s materials added to the bath is to be under~tood as part of the phosphate ionsco, ~l~nl of the bath, irrespective of the actual degree of ionization that exists in
the bath. Also, although usually less preferred because of their higher cost,
condensed phosphoric acids and their salts can be used as the source of phos-
phate ions and are to be understood as providing their stoicl-iol-,etric equivalent
2- as phosphate ions to the bath, i,.espective of their actual degree of ionization
and/or other ~lissoci?tion.
A characteristic feature of the surface ll~dll l lei 11 method accGrding to the
pl~se"l invention is that it simultaneously executes deyreasing and conversion
tredl."e.-l. Surfactant is added to the subject cleaninglconversion treatment bath
2s as the treatment component that exercises this degreasing activity. Surfactants
usable by the method accordi- ~y to the present invention are selected from the
group consisting of nonionic, cationic, anionic, and amphoteric surfactants,
wherein, however, the cG..,bindlion of cdlio~-ic surfactant with anionic surfactant
~ must be avoided because it produces problems with treal,-,en~ bath stability.
3~ Nonionic surfactants for use in the method according to the present
invention are exe,-",l;ried by polyethylene glycol-type nonionic surfactants such
as polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers, polyoxyeth-
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ylene fatty acid esters, polyoxyethylene sorbitan fatt~r acid esters, polyoxyethyl-
ene-polyoxypropyiene block polymers, and the like; polyhydric alcohol-type noni-onic surfactants such as sorbitan fatty acid esters and the like; and amide-typenonionic surfactants such as fatty acid alkylol amides and the like.
Cationic Sl,ll rd~.~nl:> for use in the method accol d~ to the present inven-
tion are exemplified by amine salt ~aliGnic sL~, racldnt~ such as higher alkyldn ,;"e
salts, polyoxyethylene higher alkylamines, and the like, and by quaternary am-
monium salt ~liGniC surfactants such as alk~ i" l~ lam",onium salts. Ampho-
teric sul ra~,ldrll~ for use in the method accordi, 19 to the present invention are ex-
emplified by amino acid amphoteric sulrdcta"l:, such as methyl alkylaminoprop-
ionate and the like and betaine amphoteric surfactants such as alkyldimethylbe-
taine and the like.
In regard to anionic surfactants for use in the method according to the
present invention, their addition and use is in many cases impaired by their typic-
ally low solubility in acidic media. However, ethylene oxide adducts, such as the
higher alkyl ether sulfate esters, can be added and utilized because they retaina good solubility even in acidic media. The preceding surfactants are suitably
added to the cleaning/conversion treatment bath in the method according to the
present invention in a concentration of approxi",dtely 0.~ to 5 g/L. I lowever, the
surfactant type and conce"lldlion should be selected as appropriate as a
function of the particular type and concentration (pick up) of the oil or greasecomponent that is to be cleaned off.
The cleaning/conversion treatment bath used in the present invention con-
tains organoperoxide. The organoperoxide has an oxidizing function and also
2s functions to induce fine-size crystal fo~-,dlion in the conversion coating. It is pre-
cisely the functions exercised by the organoperoxide that enable the surface
l,~dl",ent method according to the present invention to bring about cleaning andto form a uniform, fine, and dense conversion coating in the absence of a titani-
um colloid surface-conditioning L,e~l")ent. The use of an organoperoxide-con-
so taining cleaninglconversion treatment bath is the most characleri:,lic feature of
the method according to the present invention.
The organoperoxide used in the subject conversion treatment bath is ex-
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emplified by or~a~ ~G,~r~xides that have a simple peroxy moiety, such as tert-but-
yl hydroperuxide, di-tert-butyl per~xiJe, acetylacetone peroxide, cumene hydro-
peroxide, tert-butylpelo~ymaleic acid, and the like, and by organoperoxides thathave a percarboxylic acid moiety, such as peracetic acid, monoperphthalic acid,
persuccinic acid, and the like.
The orya"G~.er~xWe is preferably added to give a concentration from 50
to 1,00 ppm in the cleani"g/ccj, lversion l~t:atment bath. An organoperoxide con-
ce"l,dlion in the conversion l~al~ent bath below ~0 ppm can result in an inade-
quate ~cceleration of conversion coating formation and inadequate results in
~o temms of producing fine-size crystals in the cGali-~g. Concel,l,dlions in excess of
1,500 ppm do not produce any additional increments in results and are therefore
uneconomical. When the organoperoxide has a low solubility in the treatment
bath, it can be solubilized by the addition of a relatively small amount of a water-
soluble organic solvent and this can be added to the conversion treatment bath.
The organoperoxide functions as an oxidizing agent in the cleaninglcon-
version treatment bath accc: r~i"g to the present invention, and its decomposition
products will therefore accumulate in the treatment bath. For example, alcohols
are produced from hydroperoxides, alcohols and carboxylic acids are produced
from peroxy esters, and carboxylic acids are produced from percarboxylic acids.
T~e accumulation of these decomposition products does not attenuate the ef-
fects from the method according to the present invention. Accordingly, the pres-ence of these organoperoxide decG" "~ositio, ~ products in the cleaninglconversion
l,~dl"~ent baths according to the pres6"l invention from the beginning is unprob-
lematic.
The zinc phospl ~ate cleaning~conversion treatment bath used by the pres-
ent invention may also coolai~ I etchant for the purpose of generating a uniformetch of the surface of the metal being treated. When the invention method is
used to provide an underpaint coating on the metal surface, the cleani, lglconver-
sion treatment bath accordi"g to the ~r~:sent invention may also contain non-zinc
divalent metal cdliGI ,s for the purpose of generating additional improvements in
the painting performance.
Fluoride ions or cor"plex fluoride ions, e.g., fluosi' ~te ions, can be used
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as the t:lc;l ,a, ~l. Fluorine cor"~ounds that produce these ions are exemplified by
hydrofluoric acid, fll-os 'icic acid, and their metal salts (sodium salt, potassium
salt), and the etchi.)~ ion is produced by the dissolution of these compounds inthe conversion tre~ ,el It bath. The elcl~ ion is p,~rel dbly ,~ Sel)~ in the con-
version l,~l---el)t bath at a conce,-l~liG,- from 200 to 2,000 ppm.
Nickel ions, manganese ions, cobalt ions, magnesium ions, calcium ions,
and the like can be employed as the non-zinc metal ions additive. ~ach of these
types of ions can be provided by ~~issol~ltion in the conversion treatment bath of
an oxide, hyd,oxide, carbonate, sulfate, phosphate, and/or the like of the corre-
~0 sponding metal. Added metal ions are p-~r~-~bly present in the comrersion treat-
ment bath at a concentration from 200 to 3,000 ppm.
Approximately 10 to 50 ppm of trivalent iron ions will accumulate in the
treatment bath when a ~er,iren~us material such as steel sheet, etc., is being
treated, but this will not attenuate the effects of the present invention. According-
.~ Iy, tri~ralent iron ions can be unpruL,loll,dlically present in the aforesaid concel,l,d-
tion range in the cleaning/conversion treatment bath according to the present in-
vention from the very beginning.
Because the cleaning/conversion surface treatment method according to
the present invention simultaneously effects degreasing and conversion treat-
2: ment in a single step, the admixture and accumulation of a grease/oil fraction in
the treatment bath cannot be avoided during continuous treatment processes.
The permissible concentration of the oillgrease fraction in the cleaning/conver-sion treatment bath is in general approxi",alely 10 glL, although this will vary as
a function of the type and concel .lralion of the surfactant.
2s The cleaning/conversion l,edl",ent bath used by the present invention
need not contain nitric acid, nitrous acid, an organic nitro compound, etc., andin consequence thereof can be formulated as a l,edl,.,enl bath that is completely
free of nitrogenous compounds. This nitrogen-free forrnulation eliminates the
need for a nitrogenous CGI I ,,uound treatment step during effluent treatment; this
3~ makes it quite easy for the surface treatment method according to the present
invention to acco,.",.odate environmental reguldlio"s on the effluent levels of ni-
trogenous compounds.
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The standard l,t7dl",ent sequence in the surface treatment method ac-
cording to the present invention will cGIlsisl of the cleaning/conversion l~eal~,~ent
step followed by a water rinse and drain/dry steps. The water rinse can be imple-
mented as a single-step or multistep pr~cess. The final water rinse is preferably
a deio~ ed water rinse. The drainldry step is not neu3ss-~ily executed when the
metal surface will be painted, for e~.dmple, by electrodeposition, after l,eal",ent
by the method according to the present invention. Factors such as the drain/dry
temperature and time are not crucial, and drying may be conducted with heating
or at ambient temperature.
.0 Zinc phosphate conversion treatment using the surface treatment methodaccording to the present invention is ordinarily run by immersion or spraying ora combination thereof. In practice a satisfactory conversion film can be formed
using l,~:al",enttimes (contacttime between the metal surface and cleaning/con-
version treatment bath) from approximately 1 minute to approximately 10 min-
15 utes. The temperature of the cleaning/conversion treatment bath is preferably 30 ~C to 55 ~C during its contact with the metal surface being treated.
When the metal workpiece is ferriferous, the organoperoxide used in the
method according to the present invention also oxidi~es dissolved divalent iron
ions to trivalent iron ions, just as do the prior-art inorganic oxidizing agents. This
20 prevents the accumulation of divalent iron ions, which is detrimental to the con-
version reactions. Almost all of the trivalent iron ions a~forded by oxidation react
with the phosphate ion present in the conversion treatment bath to form an iron
phosphate (FePO4 ~ x H2O) sludge that is easily removed from the system.
The effects of the present invention will be illustrated below using working
examples and comparative examples of actual treatments; however, the present
invention is in no way limited by the following examples.
Examples
The test materials were cold-rolled steel sheet (SPCC-SD, sheet thick-
ness: 0.8 mm), zinc-electroplated steel sheet (sheet thickness: 0.8 mm; plating
30 weight: both surfaces 30 g/m2), galvannealed hot-dip zinc-plated steel sheet
(sheet thickness: 2.8 mm, plating weight: both surfaces 4~ glm2), and aluminum-
magnesium alloy sheet (JIS-A50~2, sheet thickness: 1.0 mm). In each case the
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sheets were cut to 70 x 150 mm to prepare the s~eciolells that were then sub-
jected to the treatments in the working and comparative examples. Each test
material was coated with 2 glm2 of a con"ner~,ial cleaninglrust-preventing oil
(NOX-~USTTM 550 from Parker Kosan Kabushiki Kaisha).
The llt:dlmerll prc,cesses co"~rl~oo to the working and comparative examp-
les are given below.
(1) cleaning/conversion treal"~ L
(The speciflc conditions are given in the respective working and compara-
tive examples.)
~0 (2) tap-water rinse
ambient temperature, 30 seconds. spray
(3) deionized water rinse
(deionized water with a conductivity of 0.2 microSiemens/cm)
ambient temperature, 20 seconds, spray
(4) drainldry: hotairat110~C, 180seconds
Each of the cleaningJconversion treatment baths used in the working and
comparative examples was adjusted to the specified free acidity using sodium
hydroxide unless spec~ied otherwise. The free acidity (in points) of the tredl",el,L
baths was the number of n,illilil~r:~ of titrant required until the color change from
20 yellow to blue when a 10 m~ sample of the t"eall"ent bath was titrated to thecolor change from yellow to blue with 0.1 N aqueous sodium hydroxide using
Bromophenol Blue as the indicator.
The conversion coating weight was measured as follows. The mass of the
treated sheet after the cleaning/conversion lleallllelll was measured to give a
2~ value in grams denoted as "W1". The codli~ Ig was then stripped off the treated
sheet using the stripping solution and sl,il,~")g conditions given below, and the
mass in grams of the stripped sheet was measured to give a value denoted as
"W2". The coating weight was then c~lc~ ted from the following equation:
coating weight in grams per square meter ("glm2") = (W1 - W2)/0.021.
30 Stripping conditions
(1) Forthe cold-rolled steel sheet
stripping solution: 5 % aqueous chromic acid
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sl~ iny conJitiGns: 75 ~C 15 minutes, i,--r,.er~ion stripping.
(2) For the zinc-piated sheet
stripping solution: 2 weight % of a"".,onium dichrc"nale + 48 weight %
of 28 % aqueous ar,l,nooia + 48 weight % of pure water.
alli~Upillg conditions: room temperature 15 minutes in,i"er:,ion stripping.
(3) For the aluminum alloy sheet
stripping solution: 5 % aqueous chromic acid
pi.,g conditions: room temperature 5 minutes immersion stripping.
The deposited coating crystals were inspected with a scanning electron
microscope (her~i-,drler usually abbreviated as "SEM") at 1 000X Ill~ylliricdlion.
This magnified image was used to evaluate basis metal coverage (presencefab-
sence of exposed suL,sl,dte) and to measure the particle size of the conversion
coating crystals for evaluation of fine-size crystal formation.
The f. Il~w;. ,9 standards were used for reporting the basis metal coverage
and the fine-size crvstal formation:
11~ Standard for evaluation of crystal particle size
I + less than 30 micrometer~ (good)
+ at least 3Q ",i_,ometers but less than 50 micrometers (moderately poor)
x at least 50 mic,.)"lelers (poor)
20 (2) Standard for evaluation of basis metal coverage
+ + absolutely no exposure of basis metal detected (good)
+ moderate exposure of basis metal detective (moderately poor)x basis metal completely exposed (poor)
EXAMPLE 1
The cleaninglconversion l,t:dl-"ent bath specified below was heated to 45
~C and used to treat cold-rolled steel sheet by i, ~ ,mer~iorl for 180 seconds. The
resulting coaLing weight was 1.2 glm2 and the fine-size crystal formation and
basis metal coverage were both ev~lu~ted as good.
Conversion Tredl"~er,l Bath
phosphate ions : 15 g/L (from addition of 75% phosphoric acid)
zinc ions : 1.3 g/L (from addition of zinc oxide)
nickel ions : 0.5 g/L (from addition of nickel carbonate~
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fluorine component : 1.0 g/L (from addition of sodium fluosilicate)
organoperoxide : 500 ppm (addition of t-butyl hydroperoxide)
tert-butanol : 4.0 g/L
SUI r~C;tdnl : 1 .0 glL
5 (The surfactant was a polyoxyethylene-polyoxypropylene block copolymer with
an average molecular weight of 10 000 and an ethylene oxide ~dclition proportionof 80 %.)
oil component : 2.0 g/L (from addition of NOX-RUSTTM 550)
free acidity : 0.6 points
EXAMPLE 2
The cleaninglconversion treatment bath of Example 1 was used to treat
zinc-eie.:t,oplated steel sheet by immersion for 180 seconds. The resulting coat-
ing weight was 3.5 g/m2 and the fine-size crvstal rc l l Il~Lion and basis metal cov-
era~e were both evaluated as good.
EXAMPLE 3
The clec...i"~/conversion treatrnent bath specified below was heated to 40
~C and used to treat cold-rolled steel sheet by spraying for 120 seconds. The re-
sulting COdtil lg weight was 1.2 glm2 and the fine-size crystal for~ lio" and basis
metal coverage were both evaluated as good.
20 Conversion Treatment Bath
phosphate ions : 14 g/L (from addition of 75 % phosphoric acid)
zinc ions : 1.3 g/L ffrom addition of zinc oxide)
cobalt ions : 0.5 glL (from addition of basic cobalt carbonate)
organoperoxide : 100Q ppm (from addition of di-tert-butyl peroxide)
tert-butanol : 2.0 g/L
first surfactant : 1.0 g/L
(The first sul r~a"l was polyoxyethylene soi bil~ll monolaurate with an average
of 20 moles of ethylene oxide ~hereinafter usually abbreviated as EO ) per mole
of sorbitan.)
second surracldnl : 0.5 g/L
(The seco"d slll ra-~nl was a salt of a partial ester of sulfuric acid with an adduct
between lauryl alcol-ol and ethylene oxide with an average of 3 moles of EO per
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mole of lauryl alcohol.)
oil component : 3.0 g/L (addition of NOX-RUSTTM 550)
free acidity : 0.5 points
EXAMPLE 4
The cleaning/conversion treatment bath of Example 3 was used to treat
galvannealed hot-dip zinc-plated steel sheet by spraying for 12Q seconds. The
resulting coating weight was 3.3 g/m2, and the fine-size crystal for"ldtion and
basis metal coverage were both evaluated as good.
E)CAMPLE ~
The cleaning/conversion treatment bath specified below was heated to 43
~C and used to treat cold-rolled steel sheet by spraying for 30 seconds and thenimmersion for 90 seconds. The resulting coating weight was 1.3 g/m2, and the
fine-size crystal fo"ndlion and basis metal coverage were both evaluated as
good.
~s Conversion Treal-"ei)t Bath
- phosphate ions : 17 g/L (from addition of 75 % phosphoric acid)
zinc ions : 1.5 g/L (from addition of zinc oxide)
fluorine component : 0.4 g/L (from addition of sodium fluoride)
organoperoxide : 100 ppm (from addition of acetylacetone peroxide)
oil component : 2.0 g/L (addition of NOX-RUSTTM 550)
firstsurfactant : 1.5 g/L
(The first surfactant was an ether alcohol corl~sponding to addition of an average
of 7 moles of EO per mole of oleyl alcohol.)
second surfactant : 0.5 g/L
2s (The second surfactant was lauryldimethylbetaine.)
free acidity : 0.7 points
E)CAMPLE 6
The conversion treatment bath of Example 5 was used to treat zinc-elec-
tlopldlt:d steel sheet by spraying for 30 seconds and then immersion for 90 sec-
onds. The resulting coating weight was 3.6 g/m2, and the fine-size crystal fonma-
tion and basis metai coverage were both evaluated as good.
EXAMPLE 7
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W ogcn7693 PCTAUS96/02678
The conversion llt:dll ~~el It bath of EXdi-~ple 5 was used to treat the alumin-um alloy sheet by spraying for 30 seconds and then immersion for 90 seconds.
The resulting codlil ~y weight was 2.~ g/m2, and the fine-size crystal formation and
basis metal coverage were both evaluated as good.
COMPARATIVE EXAMPLE 1
The conversion l-~dl,-,ent bath specified below was heated to 45 ~C and
used to treat cold-rolled steel sheet by immersion for 180 seconds. Presumably
because neither the organoperoxide nor the sul ra~t~,~l were added to this treat-
ment bath, the oil co,..,uonant was not removed even upon completion of th
~o treatment and coali"g deposition was completely absent.
Conversion Treatment Bath
phosphate ions : 15 glL (from addition of 75 % phosphoric acid)
zinc ions : 1.3 g/L (from addition of zinc oxide~
nickel ions : 0.5 g/L (from addition of nickel nitrate)
fluorine component : 1.0 g/L (from addition of sodium fluosilicate)
nitrate ions : 7.0 g/L (from addition of sodium nltrate)
nitrite ions : 100 ppm (from addition of sodium nitrite~
oil component : 2.0 glL (addition of NOX-RUSTTM 550)
free acidit,v : 0.6 points.
COMPARATIVE EXAMPLE 2
The conversion l~alment bath specified below was heated to 45 ~C and
used to treat galvannealed hot-dip zinc-plated steel sheet by immersion for 180
seconds. The resulting coating weight was 5.3 g/m2, and the basis metal cover-
age was evaluated as good. However, presumably bec~use no organoperoxide
was present, the crystal particles were coarse and fine-size crystal fol"~lion was
evaluated as poor.
~onversion Treatment Bath
phosphate ions : 15 g/L (from addition of 75 % phosphoric acid)
zinc ions : 1.3 g/L (from addition of zinc oxide)
3t~ nickel ions : 0.5 g/L (from addition of nickel nitrate~
fluorine component : 1.0 glL (from addition of sodium fluosilicate)
nitrate ions : 7.0 glL (from addition of sodium nitrate)
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W O 96~7693 PCTAUS96102678
nitrite ions : 100 ppm (from addition of sodium nitrite)
surfactant : 1.0 g/L
(The surfactant was a polyoxyethylene-polyoxypropylene block copolymer with
an average l"ol-cl~'~rweight of 10,000 and an ethylene oxide addition proportion of 80%.)
oil component : 2.0 g/L (addition of NOX-RUSTTM 550)
free acidity : 0.6 points
COMPARATIVE E)~AMPLE 3
The conversion lleaL"Iel,l bath specified below was heated to 40 ~C and
~c used to treat cold-rolled steel sheet by spraying for 120 seconds. The resulting
coating weight was 0.3 g/m2. However, presumably due to the absence of
organoperoxide, the fine-size crystal formation and basis metal coverage were
both evaluated as poor.
Conversion Treatment Bath
~s phosphate ions : 14 g/L (from addition of 75 % phosphoric acid)
zinc ions : 1.3 g/L (from addition of zinc oxide)
cobalt ions : 0.5 g/L (from addition of basic cobalt carbonate)
first surfactant : 1.0 g/L
(The first surfactant was polyoxyethylene sorbitan monolaurate with an average
of 20 moles of ethylene oxide (helei. ,drler usually abbreviated as "EO") per mole
of sorbitan.)
second surfactant : 0.5 g/L
(The second surfactant was a salt of a partial ester of sulfuric acid with an adduct
between lauryl alcohol and ethylene oxide, with an average of 3 moles of EO per
2s mole of lauryl alcohol.)
oil component : 3.0 g/L ~from addition of NOX-RUSTTM 550)
free acidity : 0.5 points
COMPARATIVE EXAMPLE 4
The conversion treatment bath specified below was heated to 40 ~C and
30 used to treat cold-rolled steel sheet by spraying for 120 seconds. The resulting
- COdlil Iy weight was 2.1 g/m2. However, presumably due to the absence of organ-
operoxide, the fine-size crystal forrnation was evaluated as poor and the basis
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metal coverage was ev~luated as "loderalely poor.
Conversion Tr~ er~t Bath
phosphate ions : 14 g/L ~from addition of 75 % phosphoric acid)
zinc ions : 1.3 g/L (from addition of zinc oxide)
cobalt ions : 0.5 g/L (from addition of basic cobalt carbonate)
chlorate ions : 1.5 g/L (from addition of sodium chlorate)
first surfactant : 1.0 9/~
(The first su, ra~ -l was polyoxyethylene sorbitan monolaurate with an average
of 20 moles of ethylene oxide (hereindrLer usually abbreviated as "EO") per mole~o of sorbitan.)
second sulra~;td~ 0.5 g/L
(The secc ncl surfactant was a salt of a partial ester of sulfuric acid with an adduct
between lauryl alcohol and ethylene oxide, with an average of 3 moles of EO per
mole of lauryl alcohol.)
~5 oil component : 3.() g/L (addition of NOX-RUSTTM 550)
free acidity : 0.5 points
COMPARATIVE EXAMPLE 5
The conversion treatment bath of Comparative Example 4 was used to
treat the aluminum alloy sheet by spraying for 120 seconds. Itowever, film depo-
sition was e, .li. ~Iy absent, presumably due to the absence of the organoperoxide.
In summary:
- Examples 1 to 7, which employed a surface treatment method according
to the present invention, were able to clean even the sur~ace of oil-coated metal
while simultaneously de~osili- ~y a unifomm, fine, and dense zinc phosphate con-
2s version coating.
- Comparati~e Exdn Ipl~ 1 involved treatment with a su~ ractal -l-free conver-
sion treatment bath, and in contrast to the above results was unable to deposit
a conversion film due to an inadequate removal of the oil/grease component.
Comparative Example 3 involved treatment with an oxidizing agent-free treat-
ment bath, while Co"~par~ e Examples 2, 4, and ~ involved treatment with or-
ganoperoxide-free baths that co--lained inorganic oxidizing agents. In these
cases, the film crystals were coarse and a uniform, fine, and dense conversion
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film was not obtained.
Benefits of the Invention
The cleaning/conversion treatment method according to the present in-
vention is able in a single step to simultaneously effect degreasing and ~inc
phosphate conversion treatment on the oil/grease-bearing surface of metals.
Moreover, it is able thereby to form a uniform, fine, and dense conversion
coating. The merits accruing to the use of the cleaning/conversion treatment
method according to the present invention can be expected to extend over a
broad range, including, for example, a substantial abbreviation of the treatment.0 sequence, simplification of the l~eal."ent facilities, space savings, i- ,creased pro-
ductivity, a reduction in reagent costs, simpliricalio" of reagent ma"agement, and
the like.
