Zagnelis™ - Zinc Aluminum Magnesium

Coating for Automotive

Rich Clausius

ArcelorMittal Global R&D

Outline

• Outline:

• Zagnelis Product Development

• Product & Process Description

• Production Capabilities

• Product Properties:

− Forming, Tool Wear, Galling, Powdering/Cracking, & Stamping

• Spot Welding

• Adhesive Bonding

• Corrosion & Corrosion Testing

− Perforation, Cosmetic, Stone Chipping, Hybrid ZnAlMg/Al Assemblies

• Outdoor/Natural Corrosion Testing

• Conclusions

10 µ m 10 µ m 10 µ m

Product Development

• Product development timeline:

− 2005 - ArcelorMittal initial lab work on ZnAlMg (ZM coatings)

− Early 2008 – Optimal coating composition defined as:

Zn, Mg 3.0%, Al 3.7% (wt %)

− Sep 2008 – First line trial Mouzon (France)

− Nov 2008 – Second line trial Eurogal (Belgium)

− June 2010 – Commercial production begins @ Eurogal

− 2nd Qtr 2012 – Commercial production begins @ Bregal

(Germany)

10 µ m 10 µ m 10 µ m

Product & Process

• Coating composition: Zn, Mg 3.0%, Al 3.7% (wt %)

Steel

ZnMgAl

(7 to 10 µ m)

Zn + Mg + Al Steel

ZnMgAl

(7 to 10 µ m)

Steel

ZnMgAl

Zn + Mg + Al

Wiping

Cooling

Hot Dip Galvanizing Process

Zagnelis – Surface Aspect

Production Capabilities

• Current product range – Available from Europe:

10 µ m 10 µ m 10 µ m

Coating Designation ZM70 ZM90 ZM120 ZM175 ZM195 ZM250 ZM310 ZM430

Coating Mass

(total both sides)

g/m2 70 90 120 175 195 250 310 430

oz/ft2 0.23 0.30 0.40 0.60 0.65 0.80 1.00 1.40

Coating Thickness (μm/per side)

5 7 10 14 16 20 25 35

Surface Treatment C (E-Passivation® CrVI-free), O (oiled)

Thickness 0.45 to 6.00 mm (0.018 to 0.236 inches)

Width Up to 1680 mm (66 inches)

Production Eurogal (Belgium) & Bregal (Germany) Lines*

* Note: Additional production sites under consideration

Potential Applications

• Automotive:

− Doors – Hem flanges can be high corrosion areas

− Deck Lids – Hem flanges & cut edge corrosion

− Hoods – Stone chipping & hem flange corrosion

− Body Sides – Cut edge corrosion & stone chipping

− Fenders – Cut edge corrosion & stone chipping

− Floor & Dash Panels – Difficult parts to form &

corrosion

− Structural & Reinforcement Parts – Cut edge &

surface corrosion

10 µ m 10 µ m 10 µ m

Product Properties & Performance

10 µ m 10 µ m 10 µ m

Tribology

• Friction behavior versus GA:

10 µ m 10 µ m 10 µ m

FUCHS 4107S – Temp. 20°C (mill oil)

FUCHS 3802-39S – Temp. 20°C (prelube)

• Zagnelis™ (ZnMgAl) coefficient of friction is generally lower than Galvanneal

(GA) for a wide range of contact pressures and two oils

• Same trend is seen at higher temperatures (64oC)

100 mm²

contact area

Tool Wear

• Tool abrasion/wear results:

− Zagnelis™ tool wear similar to EG and

HDG (GI) despite it’s a harder coating

− It is less abrasive than GA and HDG + TOC

(Thin Organic Coating)

− No Zinc pickup (same as GA)

10 µ m 10 µ m 10 µ m

EG

HDG

Zagnelis™

Galvannealed

HDG+TOC

~202 m @ 0.5 m/s

Galling

• Coating aspect after 135 mm friction length

Area in

contact

with the

tool

Area in

contact with

the tool

Area in

contact with

the tool

Area in

contact with

the tool

Area in

contact

with the

tool

Area in

contact

with the

tool

Area in

contact

with the

tool

* Note: Stick Slip is the spontaneous jerking motion & related noise that can occur when 2 objects

are sliding over each other.

Coatings without Stick-Slip* Coatings - with Stick-Slip*

Strips lubricated one time with FUCHS 4107S 400 mm² contact area

Galling

• Coating aspect after 2160 mm friction length

• Overall Zagnelis (ZnMgAl) performs best with no Stick-Slip and minimal

if any coating abrasion or scratches

Area in

contact with

the tool

Area in

contact with

the tool

Area in

contact with

the tool

Area in

contact with

the tool

Strips lubricated one time with FUCHS 4107S

Coatings without Stick-Slip

400 mm² contact area

Powdering/Cracking

• Powdering behavior

Oil: Lubrication FUCHS 4107S applied in excess

− Zagnelis™ has low powdering values which are similar to GI & EG, and much

lower than GA

Stamping

• Stamping behavior

Oil: FUCHS4107S

− Zagnelis™ coatings allow the use of higher blank hold down forces than

reference Zn coatings. Blank holder force can be similar to Zn coatings with

the use of surface treatments.

Al Al

* Note: Beta is the ratio between blank diameter before stamping and punch diameter

Spot Welding

• Spot welding range & electrode life (ZM70 & Z100):

SEP1220-2 Standard (PUDF)

Weld Current Range

Electrode Life

Electrode Life Z100 ZM70

# of Spot Welds ~465 ~465

• Slightly larger current range for 0.74 mm GI Z100 (7 µm) vs. 0.80 mm ZM70 (5.5 µm)

• Similar electrode life for Z100 & ZM70

Standard PUDF

0.65 – 0.74 mm

PUDF 0.75 – 0.84 mm

Coating GI Z100 ZM70

Steel thickness [mm] 0.74 0.80

Current [Hz] 50 50

Welding time [periods] 9 10

Holding time [periods] 6 6

Welding force [daN] 210 230

Holding force [daN] 210 230

Electrode type F16 – 5.5mm F16 – 5.5mm

Min. avg. plug

diameter [mm] 4√t=3.44 4√t=3.57

Spot Welding

• Spot welding range & electrode life (ZM70-140) :

Standard PUDF

Steel thickness [mm] 0.8

Current [Hz] 50

Welding time [periods] 10

Holding time [periods] 6

Welding force [daN] 230

Holding force [daN] 230

Electrode type F16 – 5.5mm

Min. avg. plug diameter

[mm] 4√t=3.57

SEP1220-2 Standard (PUDF)

Electrode Life ZM70 ZM100 ZM140

# of Spot Welds ~465 ~355 ~325

Weld Current Range

Electrode Life

• No difference between ZM70 (5.5 µm), 100 (8 µm), & ZM 140 (11 µm) weld current range

• Longest electrode life with ZM70

Adhesive Bonding

• Influence of Mg and Al content:

10 µ m 10 µ m 10 µ m

%Al %Mg %Al %Mg %Al %Mg %Al %Mg %Al %Mg %Al %Mg

1.5 1.5 3 3 4 3 6 3 11 3 0.3 0

Max stress

(MPa) 17.8 ± 0.2 17.4 ±0.1 19.1 ± 0.3 19.2 ± 0.4 17.6 ± 0.1 17.5 ± 0.1

Failure Mode 10%CF

90%AF

10%CF

90%AF

15%CF

85%AF

20%CF

80%AF

20%CF

80%AF

65%CF

35%AF

ZnAlMg Compositions

ZM lab samples

1496V Adhesive

• Regardless of the magnesium & aluminum content, the failure mode is similar and

primarily adhesive failure and an issue for all ZnAlMg coating compositions

• Primarily Mg & Al surface oxides, MgOx probably contribute to adhesive failure

• Note: CF = Cohesive Failure (good), AF = Adhesive Failure (bad)

steel

adhesive

Lap-shear Test

~Zagnelis Composition

Adhesive Bonding

• Crash adhesive performance (initial Zagnelis data):

10 µ m 10 µ m 10 µ m

• Depending on the crash adhesive used, results can be from good to very bad.

• Generally ZM tends to fail at the steel-adhesive interface or very near to the surface when

bonded with crash adhesives.

Crash structural adhesive

Coating Criteria 498 5089 5074 5076 1620

Zagnelis™

(ZM)

Max stress

(MPa) 21.2 19.7 21 21.3 19.7

Failure locus

(%)

60% CF

40%AF

5% CF

95%AF

90%CF

10%AD

60% CF

40%AF

5%CF

95% AF

GI

(Z)

Max stress

(MPa) 22.9 22.3 22.1 22.7 22.3

Failure locus

(%)

90%CF

10%AF

80%CF

20%AF 100% CF 100% CF

80%CF

20%AF

~ ~

0.8 mm ZM & Z

Adhesive Bonding

• Process improvement: Alkaline Activation

• With Alkaline Activation, Zagnelis™ shows improved crash adhesive performance

• Other properties such as phosphate, paint behavior, or corrosion resistance are not affected

0.8 mm ZM & Z

Crash structural adhesive Structural

adhesive

Coating Criteria 1496V 5089 1630 498 492

Zagnelis™

(ZM)

Max stress

(MPa) 23.1 22.6 24.0 25.4 23.8

Failure locus

(%) 100% CF

90%CF

10%AF 100%CF 100% CF 100% CF

GI

(Z)

Max stress

(MPa) 21.0 21.4 22.1 23.8 23.6

Failure locus

(%)

30%CF

70%AF

50%CF

50%AF

10% CF

90%AF

85% CF

15%AF 100%CF

Max Stress Improvement (Zagnelis vs. GI)

10% 6% 9% 7% 1%

Accelerated & Outdoor Exposure

Corrosion Performance

10 µ m 10 µ m 10 µ m

Automotive Corrosion

• Types of Typical Vehicle Corrosion: Visible parts

Cosmetic corrosion

Hidden parts:

Perforating corrosion

(hollow zones)

Cut edge corrosion

From scratches

Cut edges

Hidden parts

Perforating corrosion Door Flange cross section

Mean Delamination (mm) after 10 cycles (wks)

Accelerated Corrosion

• Cosmetic Corrosion – Painted Panels – VDA621-415 D

ela

min

ati

on

(m

m)

= (

wid

th-1

)/2

0,00

0,50

1,00

1,50

2,00

GA (AN2197) Z100 Z140 ZnAlMg 7µm ZnAlMg 10µm

• GA slightly better than GI Z100 with ~equivalent thickness

• Zagnelis™ is the best coating based on cyclic corrosion criteria

Accelerated Corrosion

• Perforating Corrosion Tests on Full Panels VDA 621-415 / VDA 233-102 tests Degreased samples, no phosphate treatment

VDA 621-415

0

20

40

60

80

100

0 2 4 6 8 10 12 14 16VDA cycles

Red

Ru

st

% GA HDG 10µm

EG 7,5µm ZnAlMg 10µm

0

20

40

60

80

100

0 4 8 12 16 20 24

N-VDA cycles

Re

d R

us

t (%

)

HDG 10µm

ZnAlMg 10µm

Perforating corrosion measurement (36 VDA cycles)

• Zagnelis maximum corrosion depth

10 times less compared to GI (HDG)

• Zagnelis mean corrosion depth 30

times less compared to GI (HDG)

VDA 233-102

0

200

400

600

800

1000

Att

ac

k d

ep

th (

µm

)

Mean 11 358 358

Max 81 742 854

ZnAl3.7M3 HDG 10µm GZE

Accelerated Corrosion

• Perforating Corrosion Tests on Metal/Glass Assemblies

VDA233-102 test

• Zagnelis has much less corrosion depth/pitting than GI (Z) and GA

Corrosion depth under glass flanges after 12 weeks

Zagnelis

0

100

200

300

400

500

600

700

Z 100 7 µm Z 140 10 µm GA 7 , 5 µm 7 µm

Dep

th (

µm

)

Mean Depth ( µm )

Max depth ( µm ) testing area

(without e -coat)

gap width

= 120 µm

Metal 1

Metal 2

adhesive

testing area

(without e -coat)

gap width

= 120 µm

gap width

= 120 µm

Metal

Glass

adhesive

testing area

(without e -coat)

gap width

= 120 µm

gap width

= 120 µm

Metal 1

Metal 2

adhesive

testing area

(without e -coat)

gap width

= 120 µm

gap width

= 120 µm

Metal

Glass

adhesive

Glass or 2nd Metal

Metal/Glass assembly

Accelerated Corrosion

• Stone Chipping Resistance with VDA Test:

Paint Delamination after Stone Chipping & 20 VDA621-415 Cycles

From scratches

GA 7µm GI 10µm Zagnelis™ 10µm

FLAT

DEFORMED

1.5 1.5-2.0 1.0

2.5 2.0 1.5

According to

ISO20567-1

• Zagnelis: Almost no degradation on corrosion resistance with deformation

• Zagnelis: Best stone chipped corrosion performance with & without deformation

Full

pain

t syste

m

0

50

100

150

200

250

300

350

400

450

500

550

600

650

700

0 1 2 3 4 5 6 7 8 9 10 11 12

Number of cycles

De

pth

Att

ac

k (

µm

)

Z275

ZM90

Z120

Z100

ZM120

CRS

Ma

x A

l p

itti

ng

(a

tta

ck

) d

ep

th (µ

m)

TARGET: Prevent significant

corrosion on Al for up to 12

cycles (weeks) of VDA 233-102

ZM250

Bimetallic Corrosion

• Influence of Zagnelis (ZM) Coating Thickness with Al:

From scratches

• Poor Aluminum corrosion (deep pitting) is observed with GI (Z) regardless of Zn coating thickness.

• For Zagnelis, ZM thickness affects Aluminum corrosion performance. ZM90 (7.5µm) is probably

insufficient, while ZM120 (10µm) limits Al pitting up to ~12 VDA 233-102 cycles.

Bimetallic Corrosion

• VDA 233-102 Cycles Before Significant Aluminum Corrosion (pitting depth~100µm)

From scratches

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

with CRS with Z100 with Z120 with Z275 with ZM90 with ZM120 with ZM 250

Aluminium

Nu

mb

er

of

cy

cle

s

Aluminum with

• Poor Aluminum corrosion results (~1 cycle or 7 days) are observed with GI (Z) regardless of Zn ctg. wt.

• Aluminum corrosion performance is significantly improved with Zagnelis (ZM250 or ZM120 vs. ZM90)

• Aluminum remains without any corrosion up to 20 cycles (140 days) when associated with ZM250

Bimetallic Corrosion

• Hybrid Flange Corrosion with Aluminum - GMW14872

From scratches

0

50

100

150

200

250

300

350

Al 6016 - Z120 Al 6016 - ZM120

Max

imu

m c

orr

osi

on

dep

th in

µm

68 Cycles

Underbody (UB), Exposure D 4

spray/cycle, method 1/2

• More corrosion products

developed in Al combination

with GI Z120 vs. ZM120

• Lower corrosion depths on

Al when joined to ZM120 vs.

GI Z120

Outdoor/Natural Exposure

• GI (Z) & ZM Mass Loss after 2 & 3 Years :

From scratches

GI & ZM after 3 years

0

1

2

3

4

5

6

2 years 3 years 2 years 3 years

GI 10µm ZM 11µm

co

ns

um

ed

th

ick

ne

ss

(µ

m)

MZ EC BR

GI/ZM

=3,3

GI/ZM

=2,8

GI/ZM

=2,4

GI/ZM

=2,3

GI/ZM

=2,1

GI/ZM

=2,2

• ZM appears to be the best coating in all environments - mass loss ~2 to 3 times less than GI

• With chlorides - marine site Brest, France (BR) or without chlorides - rural Maizières, France (MZ) or

urban East Chicago, IN (EC) sites

Mean and Std Dev. on

3 panels of each material

Outdoor/Natural Exposure

• GI (Z) & ZM Cut Edge /Hole Corrosion after 5 years:

• Sample evaluation at Brest

(France) - Seashore

• GI (Z): Self-healing observed

after 1 year, but protection

only lasted 1 year

• ZM: Self-healing observed

after 1 year, and continues to

last at least 4 years

• ZM self-healing duration

increased by a factor of 4

compared to GI

0

20

40

60

80

100

0 10 20 30 40 50 60

Time (months)

Am

ou

nt

of

RR

on

cu

t e

dg

es

(%

)

Z275 / 1mm ZM250 / 1mm

Zagnelis

GI

Red rust Self healing Loss of protection GI

GI Z275 Zagnelis ZM250

Pictures after 5 years

Outdoor/Natural Exposure

• Mobile Exposure on a Truck (in Europe):

Z140 – 10µm ZM120 – 10µm • Sample observations after 1

year for perforating corrosion

• Almost no change on ZM

samples while GI (Z) has red

rust in confined (test) zone

Observation after 1 year – confined (test) area

Truck driven more than

150,000 km/year,

(93,000 mi/yr) in

various environments

(road salts,…) Rack

Perforating corrosion

(test area) sample

testing area

(without e -coat)

gap width

= 120 µm

Metal 1

Metal 2

adhesive

testing area

(without e -coat)

gap width

= 120 µm

gap width

= 120 µm

Metal

Glass

adhesive

testing area

(without e -coat)

gap width

= 120 µm

gap width

= 120 µm

Metal 1

Metal 2

adhesive

testing area

(without e -coat)

gap width

= 120 µm

gap width

= 120 µm

Metal

Glass

adhesive

Cosmetic surface

sample

Outdoor/Natural Exposure

• Mobile Exposure on a Truck (in Europe):

Unpainted open panels -

Observation after 1 year

Attack depths on glass flanges after 4 years of exposure on Truck

in Sweden

0

50

100

150

200

250

300

350

400

450

ZnMg3Al3,7 10µm GI 10µm

Max A

ttack d

ep

th (

µm

)

Max 4 years

0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

Zagnelis GI

ma

ss

lo

ss

(µ

m)

Ratio

2.2

Mean and Std Dev

on 3 glass flanges

• Better corrosion performance of

Zagnelis vs. GI. Truck results similar

to static outdoor exposure in marine

& non-marine environments

ZM GI

No red rust,

only white rust

testing area

(without e -coat)

gap width

= 120 µm

Metal 1

Metal 2

adhesive

testing area

(without e -coat)

gap width

= 120 µm

gap width

= 120 µm

Metal

Glass

adhesive

testing area

(without e -coat)

gap width

= 120 µm

gap width

= 120 µm

Metal 1

Metal 2

adhesive

testing area

(without e -coat)

gap width

= 120 µm

gap width

= 120 µm

Metal

Glass

adhesive

• These results highlight the better

performance of ZM vs. GI

coatings in the field and confirm

previously observations in lab

accelerated corrosion tests

Max corrosion attack depths in

confined (test) area after 4 years

Zagnelis 10 µm GI 10 µm

Ma

x P

itti

ng

Dep

th µ

m)

Outdoor/Natural Exposure

• Mobile Exposure on a Truck (in Europe):

• Much less blistering on ZM120 vs. GI Z140

ZM120 (10µm)

Z140 (10 µm)

ZOOM

ZOOM

Scribe line width : 1 mm

Cosmetic corrosion pictures after 2 years

Conclusions

• Zagnelis (ZnAlMg) coatings have numerous

opportunities/applications due to:

− Press-shop performance

− Increased durability and robustness

− Improved corrosion protection

− Hybrid corrosion protection

− Potentially attractive alternative to batch galvanizing or

post E-coating

10 µ m 10 µ m 10 µ m

Presentations will be available

May 18 at www.autosteel.org

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