Mixed Zn/Li/Al-LDH based coa ing g own on he su ace AA7075-T6 o
imp o e i s co osion esis ance
Vale yia Kasne yk
a
,
*
, Ta siana Shulha
a
, Michal Mazu
b
, Ma ia Se dechno a
a
, Nico Scha nagl
a
,
Ca s en Blawe
a
, Mikhail L. Zheludke ich
a
,
c
,
d
a
Ins i u e o Su ace Science, Helmhol z-Zen um He eon, Gees hach 121502, Ge many
b
Depa men o Physical and Mac omolecula Chemis y, Facul y o Science, Cha les Uni e si y, P ague 212800, Czech Republic
c
Facul y o Enginee ing, CAU Kiel Uni e si y, Kiel 224143, Ge many
d
Kiel Nano, Su ace and In e ace Science (KiNSIS), Kiel Uni e si y, Kiel D-24118, Ge many
ARTICLE INFO
Keywo ds:
AA7075-T6 alloy
Laye ed double hyd oxide
Co osion p o ec ion
Con e sion coa ing
Adhesion
Func ional coa ings
ABSTRACT
Al e na i e ch omium- ee con e sion coa ings a e s ill in ocus o in e es . In his wo k, he o ma ion o mixed
Zn/Li/Al LDH-CO
32-
/OH
−
(laye ed double hyd oxide)-based mul ilaye ed CC (con e sion coa ings) was
demons a ed o he i s ime. I was g own in-si u on he su ace o AA7075-T6 aluminium alloy unde mild
condi ions (30 ◦C) in a ea men ba h con aining 0.1 M Li
2
CO
3
a pH =11.5 and in he p esence o NH
4
OH. The
Li
+
ions equi ed o he LDH s uc u e o ma ion came om he ea men ba h, while he Zn
2+
and Al
3+
we e
p o ided by he alloy dissolu ion. The o med Zn/Li/Al LDH-CO
32-
/OH
-
CC signi ican ly enhanced he co osion
esis ance o he AA7075-T6 alloy. Based on he esul s o elec ochemical impedance spec oscopy (EIS), he
o al impedance modulus |Z|a 0.01 Hz was inc eased by one o de o magni ude compa ed o he ba e subs a e,
while he sal sp ay es (SST) e ealed no pi ing a e 816 h o exposu e. These excellen p o ec i e p ope ies
we e associa ed wi h he changes o he AA7075-T6 alloy su ace du ing he LDH g ow h p ocess, o ma ion o a
passi e oxide laye wi h good ba ie p o ec ion abili y and LDH's sma nanocon aine unc ion.
1. In oduc ion
Nowadays, aluminium alloys a e widely used in he ae ospace,
au omo i e and ma ine indus ies [1–4]. Such high in e es is ela ed o
hei good s eng h- o-weigh a io and high damage ole ance. How-
e e , ope a ing condi ions o en in ol e me allic su aces coming in o
con ac wi h agg essi e media pa icula ly in ma ine and ae ospace
applica ions, which include co osi e sal s, uels, de-icing luids, and
hyd aulic luids e c [5]. This can cause co osion p ocesses, deg ada ion,
loss o in eg i y, and consequen ly a dec eased se ice li e o
aluminium-based p oduc s. The e o e, p o ec ing aluminium alloys
om co osion has become a highly impo an indus ial ask.
One o he mos e ec i e app oaches o imp o e he an ico osion
p ope ies o me allic ma e ials is o o m su ace con e sion coa ings
(CC) [6] in combina ion wi h pain applica ion. In ecen decades,
con e sion coa ings based on laye ed double hyd oxides (LDHs) ha e
been he ocus o nume ous in es iga ions. LDHs a e unc ional ma e-
ials om he class o anionic clays [7,8]. Thei s uc u es a e made o
posi i ely-cha ged mixed me al M
I
/M
III
o M
II
/M
III
hyd oxide laye s,
which a e balanced by anions (A
y−
) in e cala ed in he galle y and
sepa a ed by wa e molecules [9,10]. As cheap and en i onmen ally
iendly ma e ials, hey can ac as physical ba ie s o co osi e media
[8,11]. E en mo e, LDHs a e sma “nanocon aine s”, i.e. hey a e
capable o in e cala ing, s o ing and eleasing unc ional species on
demand, e.g. in he p esence o co osi e species o in esponse o me-
chanical damage [8,12,13].
In he con ex o co osion p o ec ion, he o ma ion o Zn/Al LDH
CC on he su ace o AA2024 alloy ha e been he subjec o ex ensi e
s udy [14–19]. These in es iga ions epo ed g owing Zn/Al LDH-NO
3
-
coa ings he AA2024 aluminium alloy su aces and subsequen ly in e -
cala ing hem wi h co osion inhibi o s, such as anada e [14–17],
molybda e, 2-me cap obenzo hiazole (MBT) [18–20] and 8-hyd oxyqui-
noline [21]. The ob ained coa ings demons a ed a high le el o co o-
sion esis ance, which was associa ed wi h he cap u e o chlo ides and
he elease o inhibi i e species, and he sel -healing abili y. As an
al e na i e o Zn/Al LDH CC, Li/Al LDH-CO
32-
/OH
-
based CC we e also
* Co esponding au ho .
E-mail add ess: [email p o ec ed] (V. Kasne yk).
Pee e iew unde he esponsibili y o Chongqing Uni e si y
Con en s lis s a ailable a ScienceDi ec
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h ps://doi.o g/10.1016/j.nanoms.2025.07.016
Recei ed 24 July 2024; Recei ed in e ised o m 27 May 2025; Accep ed 21 July 2025
A ailable online xxxx
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BY license (h p://c ea i ecommons.o g/licenses/by/4.0/).
Nano Ma e ials Science xxx (xxxx) xxx
Please ci e his a icle as: V. Kasne yk e al., Mixed Zn/Li/Al-LDH based coa ing g own on he su ace AA7075-T6 o imp o e i s co osion esis ance,
Nano Ma e ials Science , h ps://doi.o g/10.1016/j.nanoms.2025.07.016
de eloped o he AA2024 alloy [22,23]. These CC also possessed high
co osion esis ance, p ima y due o hei ba ie p o ec ion abili y.
Mo eo e , in he con ex o Li/Al LDH-CO
32-
/OH
-
o ma ion, he in-
es iga ions o P. Visse should be men ioned, who s udied he o ma-
ion o a li hium-based p o ec i e laye on he su ace o he AA2024
alloy coa ed wi h polyme coa ings con aining Li
2
C
2
O
4
o Li
2
CO
3
ille s
a e imme sion in a NaCl medium [24–29]. Unde hese condi ions,
mul ilaye ed coa ings we e o med consis ing o dense amo phous
Li-con aining pseudoboehmi e and c ys alline Li/Al LDH-CO
32-
/OH
-
phases. E en mo e, ecen in es iga ions by his g oup ha e demon-
s a ed ha his li hium-based p o ec i e laye p e o med on he
AA2024 alloy is capable o con inuing i s g ow he e ogeneously unde
co osi e condi ions [30].
In con as o he AA2024 alloy, he LDH ea men s o he AA7075
aluminium alloy a e signi ican ly less in esea ch ocus. I was i s ly
in oduced by Buchhei , who demons a ed possible o ma ion o Li
2
[Al
2
(OH)
6
]
2
CO
3
⋅nH
2
O on he su ace o AA7075-T6 alloy [22]. How-
e e , he p o ec i e abili y o he o med hyd o alci e-like coa ings was
s ill limi ed. La e on, Pe ica e al. epo ed an imp o emen o he
p o ec i e abili y o he AA7075 alloy ia in-si u g ow h o Li/Al LDH,
ollowed by subsequen elec odeposi ion o ce ium-based CC [31].
Cao e al. [32] ecen ly showed he possible o ma ion o an en i on-
men ally iendly p o ec i e coa ing on he su ace o AA7075 alloy
based on a combina ion o Zn/Al LDH CC and lignin ob ained om
biomass. Mo eo e , he hyd o he mal syn hesis o Co/Al LDH ollowed
by he in e cala ion o sodium py i hione, has been shown o imp o e
he an ico osion and an i ouling p ope ies o he AA7075 alloy.
Rega dless o he enhanced co osion p o ec ion p o ided by he LDH
o ma ion, he main disad an age o hese LDH coa ings is he syn-
hesis s a egy. The con e sion ea men in ol es he applica ion o
ele a ed empe a u es (85 ◦C o 95 ◦C) [31,32] o e en au ocla e
condi ions [33], which can signi ican ly limi hei u he applica ion,
especially a an indus ial le el. In his wo k, he o ma ion o mixed
Zn/Li/Al LDH-CO
32-
/OH
-
CC unde mild condi ions was epo ed o
he i s ime. I included ea men in a eac ion ba h con aining 0.1 M
Li
2
CO
3
a pH =11.5 in he p esence o NH
4
OH a 30 ◦C o 50 ◦C. The
cu en s udy cla i ies he p ocesses aking place on he alloy su ace
du ing he p ocess o Zn/Li/Al LDH-CO
32-
/OH
-
o ma ion and de-
elops how he ob ained Zn/Li/Al LDH-CO
32-
/OH
-
based coa ings
u he a ec co osion esis ance and adhesi e p ope ies o he
AA7075-T6 alloy.
2. Expe imen al
2.1. Subs a e
As a subs a e, AA7075-T6 aluminium alloy was used wi h he
nominal composi ion (analysed by spa k analysis, in w . %) o 90.42 %
Al, 1.53 % Cu, 0.095 % Fe, 0.16 % C , 2.43 % Mg, 0.026 % Mn, 0.058 %
Si, 0.036 % Ti, 5.17 % Zn. The samples we e cu in o pla es o 30 mm ×
40 mm ×1.6 mm o 50 mm ×50 mm ×1.6 mm ( o adhesion es s).
P io o ea men hey we e g ound wi h #1 200 and #2 500 g ades o
silicon ca bide pape , washed wi h deionised wa e and d ied a 25 ◦C in
ai .
Upscaling es s we e pe o med on he specimens wi h a size o 80
mm ×150 mm ×1.6 mm. P io o Zn/Li/Al LDH in-si u g ow h, he
AA7075-T6 specimens we e subjec ed o a cleaning p e- ea men p o-
cedu e, which includes consecu i e ea men wi h Me aclean T2001/4
VP 2 (Chemie-Ve ieb G uppe), Bonde i e C-AK ALUM ETCH 2 (Hen-
kel), and inally wi h Bonde i e C-IC Smu go NC AERO (Henkel).
2.2. Syn hesis o LDH-CO
32-
/OH
-
The Zn/Li/Al LDH-CO
32-
/OH
-
con e sion coa ings we e syn hesised
ia he p ocedu e ecen ly epo ed by S ephan e al. [23]. B ie ly, he
Zn/Li/Al LDH-CO
32-
/OH
-
was g own on he su ace o he AA7075-T6
aluminium alloy om 0.1 M Li
2
CO
3
(≥99.0 %, Sigma Ald ich) solu-
ion p ehea ed o 30 ◦C a pH =11.5 o 24 h unde con inuous s i ing.
The pH o he ea men ba h was adjus ed by adding NH
4
OH solu ion
(28 w % o 30 w %, The mo scien i ic). Zn and Al o LDH o ma ion
we e p o ided by a dissolu ion o he AA7075-T6 subs a e. In o de o
ollow he impac o syn hesis condi ions on he p o ec i e abili y o
LDH CC, specimens we e also p epa ed unde he ollowing condi ions:
30 ◦C o 12 h and 50 ◦C o 12 h. A e he ea men , he LDH-coa ed
specimens we e insed h ee imes wi h deionised wa e and d ied a
oom empe a u e in ai . The specimens we e named as LDH-N-m,
whe e N is he empe a u e o he ea men ba h in C and m is he
ea men ime in hou s.
2.3. Syn hesis ch oma e-based con e sion coa ings
Re e ence ch oma e-based con e sion coa ings we e p epa ed om
an Alodine 1 200 solu ion based on he s anda d p ocedu e desc ibed in
Re s. [34–36]. A e he ea men , he specimens we e insed wi h
deionised wa e and d ied in ai .
2.4. E alua ion o AA7075-T6 alloy dissolu ion du ing Zn/Li/Al LDH
o ma ion by in-si u a omic emission spec oelec ochemis y
The p ocess o he AA7075-T6 alloy ans o ma ion du ing Zn/Li/Al
LDH o ma ion was ollowed by in-si u a omic emission spec-
oelec ochemis y (AESEC), which was pe o med using an AME-
TEK ICP spec ome e (AMETEK, USA) connec ed o a Gam y In e ace
1 000 po en ios a (Gam y, USA) simila ly o he p ocedu e desc ibed
p e iously [37,38]. This se -up includes an in-si u cell allowing an
elec ochemical e alua ion o he p ocesses on he me allic su ace and
di ec analysis o he elemen s eleased in o he ea men solu ion. A
Spec a/Po ® 4 RC dialysis memb ane spli s up he cell o p e en he
loss o dissol ed species om he specimen du ing he elec ochemical
measu emen s. The solu ion con aining eleased ions is con inuously
ed in o he plasma using a pe is al ic pump. The emission lines o he
eleased ions a e u he analysed and compa ed wi h he elec o-
chemical da a.
P io o es , he AA7075-T6 specimens we e g ound wi h #1 200
and #2 500 g ades o silicon ca bide pape and insed wi h deionised
wa e . The exposed a ea o he me allic pla e in he AESEC cell was 0.5
cm
2
(⌀ =8 mm). The AESEC analysis was pe o med a 30 ◦C in an
elec oly e wi h a composi ion needed o LDH g ow h, i.e. 0.1 M
Li
2
CO
3
, pH =11.5 adjus ed by NH
4
OH. The elec oly e olume was
a ound 0.5 cm
3
, low a e 2 mll⋅min
−1
.
The selec i i y o Zn dissolu ion om he AA7075-T6 alloy was
calcula ed using Eq. (1) and u he plo ed as a unc ion o ime:
SZn =(nZn=nAl ) (AESEC)
(nZn=nAl ) (EDS)(1)
whe e n a e he amoun s o Zn and Al (in moles) measu ed by AESEC
du ing AA7075-T6 alloy dissolu ion, o by EDS o ini ial alloy.
The AESEC analysis demons a ed he p esence o ou s ages du ing
AA7075-T6 alloy dissolu ion. To cla i y he p ocesses aking place on he
su ace o AA7075-T6 du ing each o he s age, dissolu ion was es ed by
open ci cui po en ial (OCP) simila ly o one pe o med by AESEC, and
was in e up ed a pa icula imes, namely 422 s, 765 s, 897 s, 9 690 s,
which co espond o 1s , 2nd, 3 d, 4 h s ages espec i ely. The expe i-
men was ca ied ou in he cell wi h exposed a ea o 0.5 cm
2
(⌀ =8
mm). OCP was pe o med using a Gam y 1000 po en ios a (USA) wi h a
h ee-elec ode cell. A pla inum wi e was he coun e elec ode, a
sa u a ed Ag/AgCl elec ode was he e e ence elec ode and he
AA7075-T6 pla es we e he wo king elec odes. A e ha , he ob ained
specimens du ing 1
s
-4
h
s age o he AA7075-T6 dissolu ion we e ana-
lysed by SEM, EDS and Raman spec oscopy (see below).
V. Kasne yk e al. Nano Ma e ials Science xxx (xxxx) xxx
2
2.5. Mic os uc u al analyses
Su ace mo phology was analysed using a Vega3 SB scanning
elec on mic oscope (SEM, Tescan, Czechia) equipped wi h an ene gy
dispe si e X- ay spec ome e (EDS, Ul im Max 40 Ox o d, UK). The
mo phology o he samples was analysed in seconda y elec on SE mode,
acquisi ion was done wi h a a ol age o 8.0 kV o 10.0 kV and beam
in ensi y o 6.0 o 12.0. C oss sec ions we e analysed in back sca e ed
elec ons (BSE) mode. P io o es , he LDH specimens we e embedded
in esin, g ound h ough successi e g ades o silicon ca bide pape (#1
200, #2 500, #4 000), washed wi h deionised wa e , d ied in ai , and
spu e ed wi h ca bon. The size o he LDH lakes and he laye hick-
nesses we e es ima ed using ImageJ so wa e (Na ional Ins i u es o
Heal h) [39].
Time-o -Fligh seconda y ion mass spec ome y (TOF-SIMS) was
pe o med using SEM Tescan Ly a 3 (TESCAN GmbH, Do mund, Ge -
many) mic oscope equipped wi h equipped wi h a ToF-SIMS (To we k
C-ToF) sys em.
Scanning ansmission elec on mic oscopy (STEM) measu e-
men s we e pe o med using a JEOL JEM NEOARM-200F mic oscope
equipped wi h Scho ky ype ield-emission gun ope a ing a 200 kV.
The lamella o he sample was p epa ed in Tescan LYRA dual-beam FIB-
SEM mic oscope using he li -ou echnique, u ilizing Ga
+
ocused ion
beam. The lamella was a ached o a coppe TEM g id (EMS, USA) and
ans e ed o he STEM mic oscope. Images we e collec ed in scanning
mode using a JEOL annula da k- ield (ADF) de ec o . Ene gy dispe si e
X- ay spec oscopy (EDS) elemen dis ibu ion maps we e acqui ed
using a JEOL JED-2300 ene gy dispe si e X- ay analyse .
2.6. S uc u al cha ac e isa ion
A c ys allog aphic s udy o he LDH phase (X- ay di ac ion, XRD)
was pe o med using a D8 Ad anced Powde di ac ome e (B uke ,
Ge many). Analyses we e ca ied ou wi h Cu Kα adia ion in he ange
o 2θ om 3◦ o 60◦wi h glancing angles o 0.5◦ o 5◦, acquisi ion ime
o 10 s/s ep wi h a s ep size o 0.02◦.
Fu he s uc u al analysis o he specimens was pe o med by
Raman spec oscopy wi h a con ocal Raman mic oscope (Sen e a,
B uke , E linge , Ge many). All da a acquisi ion was pe o med a 532
nm lase wa eleng h, 20x objec i e lens, 25 mW o lase powe , 50 μm
ape u e size, and 128 scans wi h an in eg a ion ime o 4 s. E alua ion
o he ob ained Raman spec a was done using B uke OPUS 7.5.18
so wa e.
X- ay pho oelec on spec oscopy (XPS) analysis was pe o med
using a KRATOS AXIS Ul a DLD (K a os Analy ical, Manches e , Uni ed
Kingdom) equipped wi h a monoch oma ic Al Kα anode wo king a 15
kV (225 W). Fo he su ey spec a a pass ene gy o 160 eV was used,
while o he egion spec a he pass ene gy was 20 eV. The in es iga ed
a ea was 700 μm ×300 μm. Fo he samples, cha ge neu aliza ion was
necessa y. The e alua ion and alida ion o da a we e ca ied ou wi h
he so wa e CASA-XPS e sion 2.3.18. Calib a ion o he spec a was
done by adjus ing he C1s signal o 284.5 eV. Fo decon olu ion o he
egion iles, backg ound sub ac ion (linea o Shi ley) was pe o med
be o e calcula ion.
2.7. Co osion es s
Sal sp ay es s (SST) we e used o he ini ial cha ac e isa ion o
he specimen co osion esis ance. The es o small size specimens (30
mm ×40 mm ×1.6 mm) was ca ied ou using 5 w % NaCl aqueous
solu ion a 35 ◦C in a sal sp ay es chambe ClimaCORR 1000-TL FR
(VLM GmbH, Ge many) acco ding o ASTM B117 s anda d. The sam-
ples o ba e AA7075-T6 alloy, LDH-30-12 and LDH-50-12 we e sub-
jec ed o SST o 48 h, while LDH-30-24 o 816 h. The LDH-30-24
sample was egula ly isually inspec ed o co osion damages,
namely a e 48 h, 96 h, 144 h, 240 h, 336 h, 504 h, 672 h and 816 h.
Images o he co oded AA7075-T6 specimens (bo h ba e and coa ed
wi h Zn/Li/Al LDH) we e eco ded using a Canon EOS 760D came a.
The es ima ion o he co osion-a ec ed su ace (%) was made om he
ob ained pho os using ImageJ so wa e by colou -based h esholding
app oach [39]. Whe e necessa y, he su ace a eas o he ligh and da k
co osion p oduc s we e analysed sepa a ely and he inal % o
co oded su aces ep esen s he sum o bo h. The s udy o he upscaled
specimens (80 ×150 mm ×1.6 mm) was pe o med acco ding o ISO
EN 9227 es in a es chambe VLM SAL 1000-FL RS FC TA ATU CC
(VLM GmbH, Ge many) o 168 h o exposu e. All h ee upscaled
specimens we e ea ed pa allelly and we e cha ac e ised by XRD and
SEM a e SST analysis.
The u he co osion pe o mance o he AA7075-T6 specimens was
e alua ed ia elec ochemical impedance spec oscopy (EIS) in a 3.5
w % NaCl solu ion a 22 ◦C o 7 days. Measu emen s we e ca ied ou
using a Gam y 1000 po en ios a (USA) wi h a h ee-elec ode cell
comp ising a pla inum wi e coun e elec ode, a sa u a ed Ag/AgCl
elec ode and he es ing me allic pla es as wo king elec ode wi h an
exposed a ea o 0.5 cm
2
. Analysis was ca ied ou in he equency ange
om 100 kHz o 0.01 Hz a OCP, wi h 10 mV RMS sinusoidal po en ial
pe u ba ions using 9 poin s pe equency decade. The impedance da a
we e i ed using ZView so wa e, e sion 3.3c (Sc ibne , No h Ca -
olina, USA).
2.8. Adhesion es s
Th adhesion p ope ies (bo h d y and we ) we e es ed ia pull-o
adhesion and c oss-cu adhesion es s. Compa ison o he adhesion
p ope ies was pe o med o Zn/Li/Al LDH and ch oma e CC o e al-
ua e he easibili y o eplacing highly oxic ch oma e CC as well as he
pe o mance o bo h was compa ed o he ba e AA7075-T6 alloy. P io
o es ing, a wo componen s SEEVENAX p ime was applied o he 50
mm ×50 mm AA7075-T6 pla es coa ed wi h Zn/Li/Al LDH o ch oma e-
based CC. Fo ha pu pose, a wa e -based p ime SEEVENAX P ime
313–02 (Mankiewicz) was mixed wi h a ha dene SEEVENAX Ha dene
315–00 (Mankiewicz) and deionised wa e . The ob ained coa ings we e
d ied a oom empe a u e and labelled as he “d y” es . Addi ionally,
“we ” adhesion es ing was ca ied ou , which included imme sion o
he p imed specimens in deionised wa e a 40 ◦C o a pa icula ime.
D y and we pull-o adhesion es s we e pe o med in ag eemen
wi h ISO 4624 using a PosiTes AT-M manual pull-o adhesion es e
(DeFelsko, USA). Aluminium dollies (20 mm in diame e ) we e glued on
op o d ied p ime wi h A aldi e 2011 glue and d ied o 20 h. The pull-
o adhesion es s o “we ” and “d y” specimens we e epea ed h ee
imes o ep oducibili y easons.
C oss-cu adhesion es s we e pe o med based on ISO 2409 using a
TQC CC1000 es ki (TQC GmbH, Ge many). On he op o he pla es, 6
pe pendicula cu s we e made. Along o he diagonal lines, he c oss-cu
a eas we e sc ubbed wi h he supplied b ush. Adhesi e ape was applied
o one se o cu s and pulled o a a 60◦angle. In ag eemen o ISO
s anda ds, he adhesion p ope ies we e isually classi ied om 0 o 5,
whe e 0 co esponds o ull in eg i y o he coa ing, and 5 co esponds o
he emo al o mo e han 65 % o he cu a ea om he coa ing su ace.
2.9. The modynamic calcula ions
The modynamic calcula ions we e pe o med using Hyd a-
Medusa so wa e e sion o 18 Aug. 2009 o de e mine he possibili y
o Zn/Li/Al LDH o ma ion, simila ly o one epo ed in Re s. [23,40,
41]. The s abili y cons an s o all complexes we e aken om he Hyd a
da abase o Jun. 2015 [42]. The ollowing pa ame e s we e applied o
he calcula ions: ionic s eng h I =2 mol/(kg H
2
O), empe a u e =
25 ◦C, and concen a ions 100 mM o CO
3
2-
, 200 mM o Li
+
, 15 mM o
NH
4
OH, 0.1 mM o Al
3+
and 0.01 mM o Zn
2+
.
V. Kasne yk e al. Nano Ma e ials Science xxx (xxxx) xxx
3
3. Resul s and discussions
3.1. S udy o AA7075-T6 dissolu ion in 0.1 M Li
2
CO
3
a pH =11.5 in
he p esence o ammonia
P io o LDH g ow h, he p ocess o he AA7075-T6 alloy dissolu ion
in 0.1 M Li
2
CO
3
a pH =11.5 adjus ed by NH
4
OH was s udied by in-si u
AESEC. This analysis allows o simul aneously e alua e he dissolu ion
a e o selec ed elemen s and ollow elec ochemical changes occu ing
a he me allic in e ace. Fu he mo e, i is possible o obse e how he
composi ion o he ea men solu ion a ec s he a ious alloying ele-
men s o phases p esen in he alloy. [43–46]. The AESEC dissolu ion
p o iles o Al, Zn and he esul s o OCP alues a e p esen ed in Fig. 1,
o he dissolu ion p o iles o Cu and Mg in Fig. SI–1.
As i can be seen om he e olu ion o Zn, Al (Fig. 1), Cu and Mg
dissolu ion (Fig. SI–1) and he OCP, he p esence o ou s ages is
cha ac e is ic o he dissolu ion o he AA7075-T6 aluminium alloy
du ing he coa ing o ma ion. The i s pe iod, which ook place o he
i s 545 s o he AA7075-T6 pla e imme sion in he basic solu ion o
Li
2
CO
3
, was cha ac e ised by highly in ensi e dissolu ion o Al. Du ing
his s age, Al was mainly dissol ed om he su ace, which could ha e
been ela ed o he dis up ion o he passi e ilm wi h as dissolu ion o
he Al ma ix. This pe iod also included he spon aneous dissolu ion o
Cu and Mg, aking pa du ing he i s 230 s and changing o a s able
elease om he subs a e du ing all o he s ages (Fig. SI–1). Mo eo e ,
du ing he i s s age, p esence o dis inc i e spikes a 319 s (Fig. 1, g een
as e isk) was de ec ed in he p o iles o bo h Al and Zn elemen s. Such
beha iou can be explained by he elease o small Al-Zn-based in e -
me allic pa icles (IMP) om he alloy. The second pe iod unning om
545 s o 865 s was cha ac e ised by a high le el o Zn dissolu ion, which
was also accompanied by he ise o OCP. In u n, he Al concen a ion in
he solu ion d opped du ing his ime. Then, a sha p inc ease o Al
concen a ion o a alue a ound 10
−1
ppm accompanied by d ops o
bo h OCP alue and zinc concen a ion o 10
−2
ppm was obse ed in he
na ow hi d pe iod loca ed in he egion om 865 o 1 000 s. Du ing he
second and hi d s ages, p e e en ial dissolu ion o Zn om he alloy
ma ix and in e me allics occu ed, which can be especially seen om
Fig. SI–2demons a ing he selec i i y o Zn dissolu ion. The ou h
pe iod s a ed om 1 000 s demons a ed he s oichiome ic dissolu ion
o he AA7075-T6 aluminium alloy (Fig. SI–2). Mo eo e , he amoun s
o bo h Zn and Al de ec ed g adually dec eased wi h he p olonga ion o
dissolu ion ill 8 000 s. The dec ease o Al and Zn concen a ions can be
possibly ela ed o he s a ed o ma ion o a coa ing on he su ace and
i s ba ie e ec p e en ing u he as dissolu ion o he alloy. Mo e-
o e , he obse ed noncong uen changes in he Al and Zn p o iles migh
be ela ed o local pH changes a he in e ace de ining he solubili y o
he espec i e species.
To ollow he p ocesses aking place on he su ace o he AA7075-T6
alloy du ing he ou s ages o AA7075-T6 alloy dissolu ion, ou new
specimens we e p epa ed. The me allic coupons we e pu in a cell
con aining he ea men solu ion needed o LDH o ma ion and s udied
by OCP es simila ly o one du ing AESEC analysis. Once s age I-IV was
eached, he expe imen s we e in e up ed, hen he ob ained samples
we e cha ac e ised by SEM, EDS and Raman spec oscopy. Fig. SI–3
ep esen s he esul s o OCP o each specimen. As i can be ollowed
om Fig. SI–3, s age I was in e up ed a e 422 s, s age II a e 765 s,
s age III a e 897 s and s age IV a e 9 690 s.
Fig. 2demons a es he EDS elemen al dis ibu ion o Al, Zn, Cu, Fe,
Mg, O and C in he ini ial ba e AA7075-T6 alloy and he specimens
ob ained a s ages I-IV o he dissolu ion p ocess. The ba e AA7075-T6
alloy was cha ac e ised by a homogenous dis ibu ion o Al on he su -
ace, as he main componen o he alloy. Mo eo e , he p esence o Cu
and Fe con aining in e me allics can be seen on he su ace. Few spo s o
O can also be de ec ed, which we e loca ed in he a eas o he in-
e me allics. A e s a ing o he ea men , he specimen was cha ac-
e ised by less homogeneous dis ibu ion o aluminium (s age 1).
Mo eo e , a eas wi h an enhanced concen a ion o O can be also ol-
lowed. Samples ob ained du ing he pe iods II and III demons a ed an
e en less uni o m dis ibu ion o bo h Al and O on he su ace. In e -
es ingly, he ci cles wi h a dec eased concen a ion o Al and an
inc eased amoun o O we e simul aneously o med a ound he in-
e me allics. I can be p oposed ha he o ma ion o such ci cles wi h
low Al concen a ion can be ela ed o he mo e ex ensi e o ma ion o
oxidised p oduc s in he a eas close o he in e me allics. The amoun o
hese ci cles dec eased du ing he s age IV, which was ela ed o ele-
men s’ dissolu ion om he en i e su ace o he alloy as well as he
o ma ion o LDH and amo phous hyd oxides on he su ace. I should
also be men ioned, ha all 5 specimens we e cha ac e ised by a andom
dis ibu ion o he Cu-, Fe- and Mg- ich in e me allics on he su ace.
The e olu ion o he chemical composi ion o he AA7075-T6 Al alloy
su ace can be ollowed in Table 1 and SI-4 using EDS analysis a each
s age (I-IV) o LDH g ow h. As p e iously discussed, he s age I was
cha ac e ised by he selec i e dissolu ion o Al by AESEC analysis.
Howe e , he chemical composi ion o he specimen a e he s age I was
compa able o ha o he ba e AA7075-T6 alloy (Table 1). In con as ,
he specimen om he s age II was cha ac e ised by a signi ican ly
dec eased concen a ion o Al ( iz. 62.0 ±0.2 . 85.0 ±0.3 a e he
s age I) and an inc eased concen a ion o Zn (7.3 ±0.1 . 5.8 ±0.1). A
he same ime, he specimen exhibi ed inc eased concen a ions o bo h
O and C. Such obse a ions could be ela ed o he p edominan disso-
lu ion o Al aking place on he su ace du ing he s age I, and conse-
quen ly en ichmen o he su ace wi h Zn as well as wi h he low
solubili y o oxidised Zn p oduc s and he s a ing o ma ion o hy-
d oxides on he su ace. The specimen ob ained du ing he in e up ion
o he s age III showed a sligh ly inc eased concen a ion o Al, and a
dec eased amoun o Zn, which was associa ed wi h he selec i e
dissolu ion o Zn om he su ace, as i was demons a ed by AESEC. The
long- e m ea men o he AA7075-T6 alloy wi h ammonium solu ion o
0.1 M Li
2
CO
3
(s age IV) esul ed in a u he diminu ion o Al and Zn
concen a ions on he su ace accompanied wi h a ise o O amoun ,
which can be explained by he o ma ion o a con e sion coa ing on he
su ace.
Addi ionally, he su ace ans o ma ion du ing he i s ou s ages
was ollowed by Raman spec oscopy (Fig. 3). The spec a ob ained
du ing s ages I and II o he AA7075-T6 dissolu ion we e cha ac e ised
mainly by he p esence o bands in he egion o 285 cm
−1
o 650 cm
−1
associa ed wi h he Me-O ib a ion [37,47]. In u n, he p esence o
Fig. 1. AESEC dissolu ion p o iles (le y-axis) o Zn and Al plo ed oge he
wi h he OCP changes ( igh y-axis) du ing he LDH g ow h on he su ace o
AA7075-T6 o he i s 8 000 s. The inse ep esen s he egion ill 1 500 s. The
g een as e isks demons a e spikes in he p o iles, which is associa ed wi h he
elease o in e me allic pa icles.
V. Kasne yk e al. Nano Ma e ials Science xxx (xxxx) xxx
4
bands esponsible o he CO
3
2-
ib a ion was de ec ed a e longe
ea men (samples om s ages III and IV). Thus, he bands a 1 040
cm
−1
and 1 063 cm
−1
can clea ly be seen in hese wo spec a, which a e
ypical o LDH s uc u es in e cala ed wi h ca bona e ions [48–50] and
assigned o he CO
3
2-
symme ic s e ching mode. Addi ionally o ha ,
he spec um o he specimen om s age IV demons a es he p esence o
a shoulde a 1 090 cm
−1
, which is a ibu ed o he symme ic
s e ching mode o ca bona e [51]. Mo eo e , bands in he egion o 1
350 cm
−1
o 1 440 cm
−1
we e p esen in he spec a, which belong o
CO
3
2-
an isymme ic s e ching modes [52]. I should also be no ed ha
Fig. 2. EDS elemen al mappings o he ba e AA7075-T6 alloy and he specimens ob ained du ing I-IV s ages o he ea men wi h 0.1 M Li
2
CO
3
a pH =
11.5 (NH
4
OH).
Table 1
Chemical composi ions o he specimens by EDS, w . %.
Elemen /
S age
Ba e
AA7075-T6
S age I S age II S age III S age IV
Al 85.5 ±0.6 85.0 ±0.3 62.0 ±0.2 64.8 ±0.4 53.9 ±0.2
Zn 6.1 ±0.1 5.8 ±0.1 7.3 ±0.1 5.6 ±0.2 4.9 ±0.1
O0.9 ±0.1 1.1 ±0.1 16.6 ±0.1 14.1 ±0.2 26.1 ±0.1
C3.4 ±0.1 4.0 ±0.3 8.4 ±0.2 10.0 ±0.4 9.5 ±0.2
Cu 1.5 ±0.1 1.6 ±0.1 2.3 ±0.1 2.1 ±0.2 1.3 ±0.1
Fe 0.3 ±0.1 0.2 ±0.5 0.3 ±0.9 0.3 ±0.9 0.3 ±0.2
Mg 2.2 ±0.1 2.4 ±0.1 3.0 ±0.1 3.1 ±0.1 3.9 ±0.1
Fig. 3. Raman spec a o he AA7075-T6 specimens ob ained du ing I-IV s ages
o ea men wi h 0.1 M Li
2
CO
3
(pH =11.5, NH
4
OH).
V. Kasne yk e al. Nano Ma e ials Science xxx (xxxx) xxx
5
bands a 923 cm
−1
(s age IV) and a 1 003 cm
−1
(s ages III and IV) we e
de ec ed. Iden i ica ion o hese bands was icky. A li e a u e sea ch
showed ha hese bands could be a ibu ed o C-O [53] and C-C [54]
ib a ions, which could be p esen on he su ace a e he long- e m
con ac o he specimen wi h polyme ic cell used o he expe imen .
3.2. Zn/Li/Al LDH-CO
32-
/OH
-
CC s uc u e and su ace mo phology
As i was p e iously discussed, he in-si u AESEC analysis demon-
s a ed, ha Al and Zn ions a e pe manen ly eleased om he AA7075-
T6 subs a e in o he LDH ea men ba h. Consequen ly, he o ma ion
o a mixed Zn/Li/Al LDH can be assumed om a 0.1 M Li
2
CO
3
solu ion
unde he condi ions applied. To con i m his assump ion, de ailed
cha ac e isa ion o he ob ained coa ings was pe o med. Fig. 4a and
Fig. SI–5 ep esen he XRD pa e ns o he LDH coa ings g own on he
su ace o AA7075-T6. All h ee XRD pa e ns we e cha ac e ised by he
p esence o wo b oad signals loca ed a 11.5◦and 23.2◦2θ. The signals
a cu en posi ions a e ypical o he (002) and (004) e lec ions o
Li
2
Al
4
(CO
3
)(OH)
12
•3H
2
O [55,56] (PDF: 00-037-0728) as well as (003)
and (006) e lec ions o Zn
6
Al
2
(CO
3
)
16
(OH)
12
•4H
2
O [57] (PDF:
00-038-0486). As bo h ypes o LDHs ha e main cha ac e is ic signals in
he same posi ions, he iden i ica ion o he pa icula phase was limi ed
by he acili ies o he labo a o y XRD. Conce ning he impac o he
ea men condi ions, no di e ences we e obse ed in he XRD pa e ns
o he specimens ob ained a 30 ◦C a e 12 h and 24 h. In con as , he
XRD pa e n o he specimen p epa ed a 50 ◦C showed he e lec ion
peaks o LDH phase wi h signi ican ly enhanced in ensi y, which can be
associa ed o highe lakes size and he inc eased laye hickness. Such
obse a ion ag ees wi h he SEM esul s p esen ed in Figs. 4b o
d demons a ing he highes LDH c ys als size o he specimen p epa ed
a 50 ◦C o 12 h, which eached alues up o 0.5 μm. In he case o he
LDH lakes g own on he su ace o AA7075-T6 aluminium alloy a 30 ◦C
o 12 h, hei size was 2 imes smalle wi h a maximum alue o 0.2 μm.
An inc ease o he ea men ime o 24 h esul ed in u he g ow h o
he LDH c ys als, whose size was a ound 0.3 μm. Mo eo e , ega dless o
he condi ions applied o o m he coa ing, all specimens we e cha ac-
e ised by homogenous su ace co e age wi h LDH lakes. Mo eo e , o
all h ee LDH-N-m coa ings, he e we e no di e ences in he size o
shape o he LDH lakes o med on he aluminium ma ix o he in e -
me allic pa icles o he AA7075-T6 alloy. Based on he c oss-sec ion
analysis (Fig. SI–6), all h ee coa ings we e dense, bu LDH-50-12 con-
ained c acks c ossing he en i e coa ing. The hickness o he coa ings
inc eased in he ollowing o de : LDH-30-12 <LDH-30-24 <LDH-50-12
demons a ing he alues o 0.8–1 μm, 1–1.4 μm and up o 2 μm o 2.4
μm, espec i ely. I should also be men ioned ha as i was obse ed in
he case o LDH-30-12, he coa ing hickness was sligh ly lowe in he
a eas close o he in e me allic pa icles (Fig. SI–6). Mo eo e , Fig. SI–6
exhibi s EDS mapping o Al, O, Zn, C and Cu o all h ee coa ings
con i ming he inhomogeneous dis ibu ion o elemen s wi hin he LDH
coa ings. Mo eo e , EDS mapping o he LDH-30-24 su ace (Fig. SI–7)
also demons a ed ha Al, Zn, O, C, Fe, Mg and Cu we e inhomoge-
neously dis ibu ed on he su ace. Besides, Al and Zn exhibi ed he a eas
o highe concen a ion loca ed close o he Fe- and Cu-based in-
e me allics, simila ly o he one discussed p e iously o he specimen
ob ained du ing s ages II-IV o AA7075-T6 dissolu ion.
Fu he s uc u al cha ac e isa ion was done by XRD a glancing
incidence and TEM analyses. Fig. 5a ep esen s a se ies o he XRD
pa e ns o he LDH-30-24 specimen ob ained by a ying he glancing
angle om 0.5 ◦ o 5◦. A he lowes glancing angle (0.5◦), he LDH
di ac ion peak loca ed a 11.5 2θ◦was signi ican ly mo e in ensi e
compa ing o he subs a e signals, which indica es ha he LDH phase
was loca ed close o he coa ing su ace. Wi h a change o glancing angle
o 1◦, he in ensi y o he LDH signals u he inc eased, eaching i s
maximum alue. Mo eo e , he p esence o an amo phous phase was
de ec ed in he XRD pa e n. This indica es ha bo h phases we e
loca ed close o he subs a e su ace. Fu he inc ease o he glancing
angle o 1.5◦and 2◦ esul ed in a dec ease o he in ensi ies co e-
sponding o he LDH e lec ions, while he p esence o he amo phous
Fig. 4. a) XRD pa e ns o ba e AA7075-T6 aluminium alloy and he specimens coa ed wi h he LDH CCs: LDH-30-12, LDH-30-24 and LDH-50-12 ( he ull ange XRD
is p esen ed in SI). # – LDH, * – AlCuMg, •– MgZn
2,
bo h o igina ed om AA7075-T6 subs a e. SEM mic og aphs o b) LDH-30-12, c) LDH-30-24 and LDH-50-12.
V. Kasne yk e al. Nano Ma e ials Science xxx (xxxx) xxx
6
phase was s ill clea ly isible in he XRD pa e ns. I should be also
men ioned ha e iden di ac ion peaks co esponding o he subs a e
we e p esen ed in he pa e ns a a glancing angles o 0.5◦ o 2◦, indi-
ca ing ha X- ays pene a ed h ough he coa ing and eached he su -
ace o he AA7075-T6 subs a e. This is associa ed wi h in e c ys alline
su ace po osi y also demons a ed by SEM (Fig. 4), due o which X- ays
can easily pene a e o he subs a e. And he XRD spec a ob ained a
glancing angles o 2.5◦ o 5◦we e cha ac e ised by compa able in-
ensi ies o di ac ion peaks o he LDH and he subs a e.
The esul s o he TEM and TOF-SIMS analyses o he LDH-30-24
p esen ed in Figs. 5b o dag ee wi h he XRD da a ob ained a
glancing incidence and display he mul ilaye s uc u e o he Zn/Li/Al
LDH coa ing on he AA7075-T6 aluminium alloy. As i can be seen om
he TEM images (Figs. 5b and c) he s uc u e was made o h ee dis inc
laye s: a dense inne one wi h a hickness o 330–340 nm; a po ous in-
e media e laye wi h 300 nm o 310 nm hick; and a 250 nm o 280 nm
pilla laye on he op, which was cha ac e ised by a p edominan ly
e ical o ien a ion o he LDH. The hickness o he en i e coa ing was
a ound 1 μm, which is consis en wi h he esul s o SEM c oss sec ion
analysis (Fig. SI–6). Figs. 5c and d e eal EDS and TOF-SIMS elemen
dis ibu ion maps allowing o ollow he elemen al composi ion o each
laye o he coa ing. Thus, O, Al, Zn and Mg we e homogenously
dis ibu ed in he dense inne laye based on he TEM analysis. The e-
sul s ob ained by TOF-SIMS analysis a e consis en wi h he TEM anal-
ysis (Fig. 5d), which shows a homogenous dis ibu ion o Mg, Al and Li
in his laye . Howe e , his laye was mainly composed o Al, as he
concen a ions o bo h Li and Mg we e de e io a ed compa ing o Al.
Bo h TEM and TOF-SIMS showed, ha all elemen s demons a ed
inhomogeneous dis ibu ion wi hin he middle and uppe po ous laye s.
Su p isingly, magnesium was mainly loca ed in he middle laye , as can
be ollowed om Fig. 5c exhibi ing he supe posi ion o Zn and Mg. E en
mo e, Mg was nonuni o mly sp ead h oughou he laye , wi h a highe
Fig. 5. (a) XRD pa e ns o he AA7075-T6 alloy co e ed wi h he LDH-30-12 ob ained a glancing angles 0.5◦ o 5◦; (b)–(c) c oss sec ion TEM mic og aphs o he
LDH-30-24 coa ing a di e en magni ica ion and he co esponding EDS mappings o he elemen al dis ibu ion o O, Al, Zn and Mg; (d) TOF-SIMS maps (side iew)
o Li
+
, Mg
+
, Al
+
.
V. Kasne yk e al. Nano Ma e ials Science xxx (xxxx) xxx
7
concen a ion close obse ed close o he pilla -po ous laye s in e ace.
The TOF-SIMS p o ile o Mg, p esen ed in Fig. SI–8, also demons a ed a
simila dis ibu ion o Mg h oughou he coa ing. In u n, TOF-SIMS
mapping and p o iles o Li and Al (Fig. 5d Figs. SI-8a and c), e ealed
ha he op laye was made o Li and Al, whose concen a ions we e
enhanced in his laye o he coa ing. Based on he esul s o he bo h
analyses, i can be p oposed ha ha he dense laye was made o
amo phous hyd oxides, like amo phous Li-pseudoboehmi e and
Fig. 6. XPS spec a o he AA7075-T6 aluminium alloy coa ed wi h LDH CC a 30 ◦C o 24 h. (a) ull su ey spec um, (b) Al 2p, (c) C 1s, (d) Li 1s, (e) O 1s, ( ) Zn 2p.
V. Kasne yk e al. Nano Ma e ials Science xxx (xxxx) xxx
8
amo phous Al(OH)
3,
in a manne simila o he con e sion laye o med
on he su ace o he AA2024 alloy by li hium-leaching om a poly-
u e hane coa ing [26,58]. In u n, he middle laye appa en ly ep e-
sen s a combina ion o amo phous phases, mainly amo phous Mg(OH)
2
,
and c ys alline LDH. And he op pilla laye was made by Zn/Li/Al LDH
lakes composed o Zn, Al, Li and O, espec i ely.
TEM analysis p o ed he p esence o Zn and Al in he LDH lakes
g own on he su ace o he AA7075-T6 aluminium alloy. To unde s and
whe he mixed Zn/Li/Al LDH was ob ained unde he ea men con-
di ions, XPS analysis was pe o med. XPS allows o in es iga e he
p esence o he elemen s in dep h o he coa ing. Fig. 6 ep esen s he
XPS spec um o LDH-30-24: (a) shows he ull su ey spec um, while
(b) o ( ) ep esen he selec ed egions o he elemen s. The egion
spec um o O 1s p esen ed wo signals loca ed a 531.2 eV and 531.6
eV, which a e a ibu ed o he CO
3
2-
g oup [59] and Al
2
O
3
. The C 1s
egion spec um con ains h ee peaks a app oxima ely 284.6 eV, 286.1
eV and 288.3 eV asc ibed o C-C, C-O, and O-C=O, espec i ely. The i s
wo signals a e a ibu ed o ad en i ious ca bon con amina ion om
he en i onmen , while he las one was cha ac e is ic o CO
3
2-
. Two
peaks a 73.7 eV (Al 2p 3/2) and 74.2 eV (Al 2p 1/2) we e p esen in he
egion spec um o Al 2p and co espond o na i e Al
2
O
3
. The Zn 2p
spec um con ains signals o Zn 2p1/2 a 1 044.7 eV and Zn 2p3/2 a
1 021.6 eV a ibu ed o Zn
2+
species o igina ed om Zn/Al LDH [19,
60]. The Li 1s egion spec um is cha ac e ised by a b oad signal o low
in ensi y a 54.9 eV, which can be associa ed o Li being su ounded o
Zn and Al. Consequen ly, based on he esul s o he XPS and TEM an-
alyses, a mixed Zn/Li/Al LDH-CO
32-
/OH
-
was c ys allised on he su ace
o he AA7075-T6 alloy.
3.3. Co osion pe o mance
The co osion p o ec i e abili y o he ob ained Zn/Li/Al LDH
coa ings was i s ly e alua ed by sal sp ay es (SST). Fig. 7 ep esen s
he pho os o he ba e AA7075-T6 aluminium alloy and he specimens
coa ed unde di e en condi ions a e 48 h o SST. Mo eo e , he
e olu ion o he co osion p opaga ion o he LDH-30-24 sys em o
816 h is also demons a ed.
The ba e AA7075-T6 specimen was highly co oded al eady a e 48
h o exposu e, a ound 68 % o he su ace was co e ed by he co osion
p oduc s. In u n, he specimens coa ed wi h Zn/Li/Al LDH we e
signi ican ly less co oded. Mo eo e , he p o ec i e abili y o he con-
e sion coa ing s ongly depended on he condi ions o he in-si u g ow h
o he LDH laye . Among all h ee specimens, he leas p o ec i e was he
one p epa ed unde an ele a ed empe a u e (LDH-50-12), demon-
s a ing 40 % o he damaged su ace a e 48 h o SST. Such de e io a ed
beha iou can be ela ed o he p esence o he c acks in he coa ing
demons a ed by he c oss-sec ion analysis (Fig. SI–6). Only 27 % o he
su ace was co oded in he case o he coa ing in-si u g own a a lowe
empe a u e o he same ea men ime (LDH-30-12). In u n, a sig-
ni ican imp o emen in p o ec i e abili y was de ec ed o he Zn/Li/Al
LDH coa ing syn hesised a 30 ◦C o 24 h, which showed almos no
p esence o isible co osion p oduc s a e 48 h o SST. Fu he p o-
longa ion o he exposu e ime demons a ed ha he appea ance o he
i s isible co osion p oduc s was seen only a e 96 h (4 % o co oded
su ace). Besides, he p esence o da k poin s was also obse ed on he
su ace wi h u he p olonga ion o he SST up o 144 h (highligh ed by
yellow in Fig. 7). Fu he p olonga ion o he SST esul ed in he slow
deg ada ion o he AA7075-T6 specimen coa ed wi h Zn-Li/Al LDH-
Fig. 7. Pho os o ba e AA7075-T6 aluminium alloy, LDH-30-12 h and LDH-50-12 subjec ed o SST o 48 h, and he e olu ion o SST pho os o he LDH-30-24 h
specimen (48 h o 816 h). The numbe s in he pho os ep esen he amoun o co oded su ace (in %) es ima ed using ImageJ so wa e.
V. Kasne yk e al. Nano Ma e ials Science xxx (xxxx) xxx
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