P. 1 Химподготовка с высокой степенью травления & рекомендации Qualicoat Estal Belgium Семинар Antwerp 21 th aug. 2000 ETCHING

p. 1

Химподготовка с высокой степенью травленияХимподготовка с высокой степенью травления&

рекомендациирекомендации Qualicoat Qualicoat

Estal BelgiumEstal Belgium Семинар

Antwerp 21th aug. 2000

ETCHING the SENSITIVE LayerETCHING the SENSITIVE Layer

ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1

p. 2

Рекомендации Рекомендации Qualicoat :Qualicoat :““При подготовке рекомендуется снимать как минимум При подготовке рекомендуется снимать как минимум 2 2

гг//мм² ² алюминия с поверхности для удаления т.н. алюминия с поверхности для удаления т.н. специфического «чувствительного слоя», чтобы свести к специфического «чувствительного слоя», чтобы свести к

минимуму риск появления нитевидной коррозии!минимуму риск появления нитевидной коррозии!””““Начиная с сентября 2000 г., новые линии должны Начиная с сентября 2000 г., новые линии должны

обеспечиватьобеспечивать 22гг//мм², ², а для действующих линий а для действующих линий рекомендовано выдерживать по крайней мере рекомендовано выдерживать по крайней мере 1 1 гг//мм²” ²”

Травление «чувствительного» слояТравление «чувствительного» слоя


p. 3

Цель семинараЦель семинара::

1° 1° Дать объяснение понятия Дать объяснение понятия «подготовка под конверсию»«подготовка под конверсию»..

2° 2° Что мы имели и каковы наши Что мы имели и каковы наши возможности, основанные на возможности, основанные на сегодняшнем сегодняшнем “know-how” ?“know-how” ?



p. 4

Цель семинараЦель семинара::

3° “3° “How can we realise a synergetic effect by How can we realise a synergetic effect by putting together the opportunities of :putting together the opportunities of :

the Al-substrate-suppliers,the Al-substrate-suppliers,the Qualicoat (job-)coaters,the Qualicoat (job-)coaters,

the Al-constructors,the Al-constructors,and the architectural end-users,and the architectural end-users,

to eliminate (to eliminate (ETCHETCH) the FFC () the FFC (SENSITIVE LAYERSENSITIVE LAYER) ?” ) ?”



p. 5

The position of the (job-)Coater :The position of the (job-)Coater :



MetallurgistsAl-extrusions

Al-parts

Chemistspretreatment-

chemicals

Chemistsorganic

coatings

ConstructorProcess

equipment

Constructorassembling

coated Al-parts

End-userprofessionalor private

(job-)CoaterAl-substrates,

treated in an Equipentusing pretreatment

chemicals & organic coatings

Estal &specialistsrecommendations

& advise“We all”

p. 6

The position of the (job-)Coater :The position of the (job-)Coater :



Estal &specialistsrecommendations

& advise“We all”

The (job-)Coater is specialist in applied surface treatment ; this activity is based on Technologies of specialists in :

* Metallurgy (Al-substrate suppliers)* Chemistry (pretreatment-chemicals suppliers,

organic coating suppliers,environmental process suppliers)

* Constructions (process-equipment &engineering)

p. 7

AluminiumChemical pre-treatmentwith higher etch-grade

Подготовка под конверсию:Строительный рынок

1999

ref.: Etchgrade9903.ppt WvH 05ma99


p. 8

В процессе подготовки под конверсию,алюминиевая поверхность обрабатывается до

состояния, которое называют - “химически чистая поверхность”

для подготовки поверхности под последующее конверсионное покрытие.

Цель подготовки под конверсию


p. 9

Алюминиевые субстраты характеризуются “загрязнениями” в зависимости от происхождения:

•органические (масло, жир и т.п.)•неорганические (оксиды, пыль и т.п.)

•термо-механические (экструзия и примеси) (как глубоко? & Какого сорта загрязнения?)

Органические загрязнения уничтожаются методом “обезжиривание”,

неорганические методом “травления”

Основополагающие Принципы:


p. 10

Degreasing is “state of the art” if the surface is “wetted” with a waterfilm” after rinse ;

most of the used oils are easy to eliminate.Etching is “state of the art” if the “superficial

impurities” are eliminated ; the impurities that are possible to eliminate in a chemical process are

disappeared when enough substrate-layer is etched.Chemical etching can be executed :

in alkaline and/or in acid etching-solutions.

Как обезжирить и насколько глубоко травить?


p. 11

Alkaline etchers are used in anodising lines for reasons of their fast and strong “cleaning” working in the dept and

specifically to realise a so called E6 - aspect (= esthetical desired finishing)

as a pre-treatment forthe followed anodising step.

Alkaline etchers realise heavyenvironmental problems (air pollution on the process baths,

more waste water and volumetric sludge quantities) !

Alkaline and/or acid etching : etching-grade ?


p. 12

In the case of conversion coating (chromate- or Cr-free)it is enough to realise a “chemical clean surface”,

here the E6 - aspect is not a demand.For that reason, in de pre-conversion

(pre-treatment before chromate- or Cr-free-coating), “less-environmental-polluting” acid etchers are used which have the supplemental characteristic that they can be used

combined with wetting components at lower temperatures and they produce less sludge.



p. 13

Light extrusion-stripes (roughness in the material) will be an unacceptable esthetical lack after anodising, for

that reason a deeper etch is used.

In the conversion coating before organic coating(50-150 µm) this “esthetical roughness” is easier to

“equalise” by the relative thick non-transparent paint-layer.



p. 14

Special Henkel ST acid etchers with an etch-gradefrom < 1g/m² till > 3 g/m² in the degrease-deoxidise step

transform the surface to such a condition that the surface can be nominated as “chemical clean”.

Impurities, situated deeper on the crystal-borders and/or impurities of elemental rests in the Al-alloy are not eliminated

neither in alkaline, nor in acidic solutions.



p. 15

In de chemical pre-treatment, the job-coaters’ possibilities are limited till “surface-treatment” and the industrial pre-

treatment lines don’t have the possibility to eliminate those “deep-situated” or “in the alloy integrated” impurities.

An heavier etch than 8 g/m² gives no better quality when used before a conversion coating ;

an heavier etch produces more “environmental” pollution (waste water & disposal sludge).



p. 16

Comparative tests proved that in the pre-conversion only a negligible quality difference is realised by

acidic etch or

alkaline etch followed by acidic neutralising.

Al-1000-series : OH > H+Al-3000-series : OH = H+

Al-5000-,6000-,8000-series : OH < H+



p. 17

In the specific case of conversion coating, where no correcting sulphuric acid-treatment step is used like by

anodising, an alkaline strong etching can even realise poor conversion-layers !

Alkaline etchers realise more roughness (higher individual pointed potential charge) on the surface, while acidic etchers realise a qualitatively better equalised (lower flat potential

charge) surface.



p. 18

Sharp “points” can penetrate the “very thin conversion layer” and can perforate this layer (< 0,5 µm)

in the water dry-off stage.This can result in a conversion coating that is “ not totally

sealed” and where the pointed extremities can oxidise easier due to external (corrosive) influences.

Alkaline etchers can bring residuals of aluminate rests (in capillary thermal insulation joints !), that raise difficulties by

insufficient acid neutralising.



p. 19

Environmental goals with “less pollution on the source” and/or the European and local prescriptions like

“State of the art” (Eur)“BBT” = Vlarem = “Best Beschikbare Technieken”

“Stand der Technik” = D, etc… will bring the sector of surface pre-treatment in the coming

future to such processes that less waste-water and less disposal (sludge) are produced.



p. 20

Especially caused by those environmental restrictions and prescriptions and the following environmental consequences

(extreme high taxes) willcause a selection of such a surface treatment thatan optimised equilibrium can be realised between

“enough quality assuredenough quality assured”

and“to much = industrial to expensiveto much = industrial to expensive”.



p. 21

J. H. Nordlien reported the results of the research carried out by SINTEF Materials Technology Laboratories and

NTNU (Norwegian University of Science and Technology)In this study the depth of the impurities is located

between 0.2 - 1 µm.L’ADAL of France proposed a few years ago the

“Système Maritime” where an etch grade of >8 g/m² (alkaline & acid combination) was prescript.

How strong etching ? 1 g/m² or 2g/m² or 8 g/m² or xx g/m² ?


p. 22

How to define an etch-grade ?

An etch-capacity of 600g/m².h means :“in the etch-solution

a weight-loss CAPACITY of 600 g is measured after a treatment time of 1h (60minutes)

at a prescript temperature and a prescript free chemical concentration for each defined chemical m² surface-area”



p. 23

Beizen - Abtrag - Temperatur

Temperatur°C

Abtrag g / m² * h

45 50 55 60 65 70 75 800

500

1.000

1.500

2.000

2.500

3.000

3.500

4.000

50 g / l NaOH

100 g / l NaOH

150 g / l NaOH

200 g / l NaOH

ref.: Etchgrade9903.ppt WvH 05ma99 ref.: J. Lindener Henkel ST-T (Beizen)

+/- 16 à 17 g/min+/- 80 g/m² (4 à 5 min.)+/- 30 µm

p. 24

An etch-grade of 2g/m² means :“in the pre-conversion-step, a loss of 2g is measured for each

defined chemical m² surface-area”or

“an Al-part (Al sp.gr. 2698.9 @ 20°C) with dimensions (f.i.) 0,5m x 1m (thickness = 1mm=1000µm)

has a chemical surface-area (recto + verso) of 1,003 m²and losses 2 g after etching = 1 g recto (0.5m²) + 1 g verso (0.5m²)

or losses in depth ca. 0,74 µm0,74 µm recto + 0,74 µm0,74 µm verso”.



p. 25

or

“an Al-part with dimensions (f.i.) 1m x 1m (thickness = 1mm=1000µm)

has a chemical surface-area (recto + verso) of 2,004 m²and losses 4 g after etching = 2 g recto + 2 g verso

or losses in depth ca. 0,74 µm0,74 µm recto + 0,74 µm0,74 µm verso”,or

“an Al-sample part with dimensions(f.i.) 0,25m x 0,1m (thickness = 2mm=2000µm)

has a chemical surface-area (recto+verso) of 0,051 m²and losses 0,1028 g after etching = 0,0514 g recto + 0,0514 g verso

or losses in depth ca. 0,76 µm0,76 µm recto + 0,76 µm0,76 µm verso”



p. 26

The roughness of an extruded aluminium part is higher than a few µm !

This roughness is NOT physical eliminatednor equalised by etching !

Only the visual appearance is optical changed to an esthetical accepted E6-result !

Some crystals can be eliminated by strong etching to leave a pit = dull = lustreless !

(Henkel ST / R&D)



p. 27

Only if the sector of surface-treatment on aluminium parts for architectural use

can be informed exactly of the depth of the so called “sensitive layer”

based on metallurgic science R&D, the (job-)coaters can steer the chemical etch-grade till such a deepness that the treatment still is a “surface” treatment, with the goal to condition the surface part to a chemical clean substrate

as a step before conversion coating !



p. 28

At the ESTAL-congressAt the ESTAL-congresssept. 1999 / Dresden,sept. 1999 / Dresden,

a presentation was given,a presentation was given, based on a specialist metallurgic based on a specialist metallurgic

R & D programR & D programon extrusion-parts ofon extrusion-parts of

AA 6060/6063AA 6060/6063



p. 29

EN 573-3:1994 (composition of Al-alloys)EN 573-3:1994 (composition of Al-alloys)



Nr.Chem. Symb.

EN AW-6060 EN AW-AlMgSi

EN AW-6063EN AW-AlMg0,7Si

Si

0,30-0,6

0,20-0,6

Fe

0,10-0,30

0,35

Cu

0,10

0,10

Mn

0,10

0,10

Mg

0,35-0,6

0,45-0,9

Cr

0,05

0,10

Zn

0,15

0,10

Ti

0,10

0,10

Sol.(*)

0,05

0,05

Tot.(**)

0,15

0,15

Al

rest

rest

(*) & (**) : Sol = other single additive ; Tot. = total of all other additives

p. 30

EN 573-3:1994 (composition of Al-alloys)EN 573-3:1994 (composition of Al-alloys)



Nr.Chem. Symb.

EN AW-6060 EN AW-AlMgSi

EN AW-6063EN AW-AlMg0,7Si

Si

0,30-0,6

0,20-0,6

Cu

0,10

0,10

Sol.(*)(Pb)

0,05

0,05

Al

rest

rest

1° Conclusion “small risk if” : Si > 0,55% ; Cu > 0,02 % ; Pb > 0,022% “ou en dehors des spécifications des alliages AA 6060/6063”

p. 31



2° Conclusion :“The important attack (access) by a FFC, observed during the corrosion trials is imputed to a reactive layer on the surface extremities,owning a chemical not to predict composition,of which the formation is explained by the thermo-mechanical treatment of the alloy.It is approved that by :

eliminating at least 2 g/m² of the metal by a chemical etch,followed by a ‘state of the art’ chromate coating,

the extrusions realised in the alloys AA 6060/6063 gave a high resistance against filiform corrosion”.

p. 32



Cu

Mg

Si

?

Mg

SiFe

Cu

?

Sensitiv layer : ca. 0.75 µmwith higher % of elements

AA 6060/6063with normal % of elements

Organic pollution

Dust pollution

p. 33



Cu

Mg

Si

?

Mg

SiFe

Cu

?



Rinse water filmafter degreasing

p. 34



Cu

Mg

Si

?

Mg

SiFe

Cu

?



Conversion coatingincl. impurities,if not etched !

p. 35



Cu

Mg

Si

?

Mg

SiFe

Cu

?

Sensitiv layer : ca. 0.75 µmeliminated


Conversion coatingchemical pure,if perfect etched !

Documents

P. 1 Химподготовка с высокой степенью травления & рекомендации Qualicoat Estal Belgium Семинар Antwerp 21 th aug. 2000 ETCHING