P. 1 Химподготовка с высокой степенью травления & рекомендации Qualicoat Estal Belgium Семинар Antwerp 21 th aug. 2000 ETCHING the SENSITIVE Layer ref.: - презентация

1 p. 1 Химподготовка с высокой степенью травления & рекомендации Qualicoat Estal Belgium Семинар Antwerp 21 th aug ETCHING the SENSITIVE Layer ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1

2 p. 2 Рекомендации Qualicoat : При подготовке рекомендуется снимать как минимум 2 г/м² алюминия с поверхности для удаления т.н. специфического «чувствительного слоя», чтобы свести к минимуму риск появления нитевидной коррозии!При подготовке рекомендуется снимать как минимум 2 г/м² алюминия с поверхности для удаления т.н. специфического «чувствительного слоя», чтобы свести к минимуму риск появления нитевидной коррозии! Начиная с сентября 2000 г., новые линии должны обеспечивать 2г/м², а для действующих линий рекомендовано выдерживать по крайней мере 1 г/м²Начиная с сентября 2000 г., новые линии должны обеспечивать 2г/м², а для действующих линий рекомендовано выдерживать по крайней мере 1 г/м² Травление «чувствительного» слоя ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1

3 p. 3 Цель семинара: 1° Дать объяснение понятия «подготовка под конверсию». 2° Что мы имели и каковы наши возможности, основанные на сегодняшнем know-how ? Травление «чувствительного» слоя ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1

4 p. 4 Цель семинара: 3° How can we realise a synergetic effect by putting together the opportunities of : the Al-substrate-suppliers, the Qualicoat (job-)coaters, the Al-constructors, and the architectural end-users, to eliminate (ETCH) the FFC (SENSITIVE LAYER) ? to eliminate (ETCH) the FFC (SENSITIVE LAYER) ? Травление «чувствительного» слоя ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1

5 p. 5 The position of the (job-)Coater : ETCHING the SENSITIVE Layer ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1 Metallurgists Al-extrusions Al-parts Chemists pretreatment- chemicals Chemists organic coatings Constructor Process equipment Constructor assembling coated Al-parts End-user professional or private (job-)Coater Al-substrates, treated in an Equipent using pretreatment chemicals & organic coatings Estal & specialists recommendations & advise We all

6 p. 6 The position of the (job-)Coater : ETCHING the SENSITIVE Layer ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1 Estal & specialists recommendations & 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)

7 p. 7 Aluminium Chemical pre-treatment with higher etch-grade Подготовка под конверсию : Строительный рынок 1999 ref.: Etchgrade9903.ppt WvH 05ma99 ETCHING the SENSITIVE Layer

8 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 ref.: Etchgrade9903.ppt WvH 05ma99

9 p. 9 Алюминиевые субстраты характеризуютсязагрязнениями 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 методомобезжиривание, неорганические методом травления Основополагающие Принципы : ref.: Etchgrade9903.ppt WvH 05ma99

10 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? ref.: Etchgrade9903.ppt WvH 05ma99

11 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 for the followed anodising step. Alkaline etchers realise heavy environmental problems (air pollution on the process baths, more waste water and volumetric sludge quantities) ! Alkaline and/or acid etching : etching-grade ? ref.: Etchgrade9903.ppt WvH 05ma99

12 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. Alkaline and/or acid etching : etching-grade ? ref.: Etchgrade9903.ppt WvH 05ma99

13 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 ( µm) this esthetical roughness is easier toequalise by the relative thick non-transparent paint-layer. Alkaline and/or acid etching : etching-grade ? ref.: Etchgrade9903.ppt WvH 05ma99

14 p. 14 Special Henkel ST acid etchers with an etch-grade from 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. Alkaline and/or acid etching : etching-grade ? ref.: Etchgrade9903.ppt WvH 05ma99

15 p. 15 In de chemical pre-treatment, the job-coaters possibilities are limited till surface-treatment and the industrial pre- treatment lines dont have the possibility to eliminate thosedeep-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). Alkaline and/or acid etching : etching-grade ? ref.: Etchgrade9903.ppt WvH 05ma99

16 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+ Alkaline and/or acid etching : etching-grade ? ref.: Etchgrade9903.ppt WvH 05ma99

17 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. Alkaline and/or acid etching : etching-grade ? ref.: Etchgrade9903.ppt WvH 05ma99

18 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. Alkaline and/or acid etching : etching-grade ? ref.: Etchgrade9903.ppt WvH 05ma99

19 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. Alkaline and/or acid etching : etching-grade ? ref.: Etchgrade9903.ppt WvH 05ma99

20 p. 20 Especially caused by those environmental restrictions and prescriptions and the following environmental consequences (extreme high taxes) will cause a selection of such a surface treatment that an optimised equilibrium can be realised between enough quality assuredenough quality assured and to much = industrial to expensiveto much = industrial to expensive. Alkaline and/or acid etching : etching-grade ? ref.: Etchgrade9903.ppt WvH 05ma99

21 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 µm. LADAL 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 ? ref.: Etchgrade9903.ppt WvH 05ma99

22 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 How strong etching ? 1 g/m² or 2g/m² or 8 g/m² or xx g/m² ? ref.: Etchgrade9903.ppt WvH 05ma99

23 p. 23 Beizen - Abtrag - Temperatur Temperatur°C Abtrag g / m² * h 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

24 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. 20°C) with dimensions (f.i.) 0,5m x 1m (thickness = 1mm=1000µm) has a chemical surface-area (recto + verso) of 1,003 m² and losses 2 g after etching = 1 g recto (0.5m²) + 1 g verso (0.5m²) 0,74 µm0,74 µm or losses in depth ca. 0,74 µm recto + 0,74 µm verso. How strong etching ? 1 g/m² or 2g/m² or 8 g/m² or xx g/m² ? ref.: Etchgrade9903.ppt WvH 05ma99

25 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 m² and losses 4 g after etching = 2 g recto + 2 g verso 0,74 µm0,74 µm or losses in depth ca. 0,74 µm recto + 0,74 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 m² and losses 0,1028 g after etching = 0,0514 g recto + 0,0514 g verso 0,76 µm0,76 µm or losses in depth ca. 0,76 µm recto + 0,76 µm verso How strong etching ? 1 g/m² or 2g/m² or 8 g/m² or xx g/m² ? ref.: Etchgrade9903.ppt WvH 05ma99

26 p. 26 The roughness of an extruded aluminium part is higher than a few µm ! This roughness is NOT physical eliminated nor 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) How strong etching ? 1 g/m² or 2g/m² or 8 g/m² or xx g/m² ? ref.: Etchgrade9903.ppt WvH 05ma99

27 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 calledsensitive 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 ! How strong etching ? 1 g/m² or 2g/m² or 8 g/m² or xx g/m² ? ref.: Etchgrade9903.ppt WvH 05ma99

28 p. 28 At the ESTAL-congress sept / Dresden, a presentation was given, based on a specialist metallurgic based on a specialist metallurgic R & D program on extrusion-parts of AA 6060/6063 ETCHING the SENSITIVE Layer ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1

29 p. 29 EN 573-3:1994 (composition of Al-alloys) ETCHING the SENSITIVE Layer ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1 Nr. Chem. Symb. EN AW-6060 EN AW-AlMgSi EN AW-6063 EN AW-AlMg0,7Si Si 0,30 -0,6 0,20 -0,6 Fe 0,10 -0,30 0,35 Cu 0,10 Mn 0,10 Mg 0,35 -0,6 0,45 -0,9 Cr 0,05 0,10 Zn 0,15 0,10 Ti 0,10 Sol. (*) 0,05 Tot. (**) 0,15 Al rest (*) & (**) : Sol = other single additive ; Tot. = total of all other additives

30 p. 30 EN 573-3:1994 (composition of Al-alloys) ETCHING the SENSITIVE Layer ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1 Nr. Chem. Symb. EN AW-6060 EN AW-AlMgSi EN AW-6063 EN AW-AlMg0,7Si Si 0,30 -0,6 0,20 -0,6 Cu 0,10 Sol. (*) (Pb) 0,05 Al 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

31 p. 31 ETCHING the SENSITIVE Layer ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1 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.

32 p. 32 ETCHING the SENSITIVE Layer ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1 Cu Mg Si ? Mg Si Fe Cu ? Sensitiv layer : ca µm with higher % of elements AA 6060/6063 with normal % of elements Organic pollution Dust pollution

33 p. 33 ETCHING the SENSITIVE Layer ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1 Cu Mg Si ? Mg Si Fe Cu ? Sensitiv layer : ca µm with higher % of elements AA 6060/6063 with normal % of elements Rinse water film after degreasing

34 p. 34 ETCHING the SENSITIVE Layer ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1 Cu Mg Si ? Mg Si Fe Cu ? Sensitiv layer : ca µm with higher % of elements AA 6060/6063 with normal % of elements Conversion coating incl. impurities, if not etched !

35 p. 35 ETCHING the SENSITIVE Layer ref.: Estal BE 2000.ppt WvH 14 jul 00 - draft 1 Cu Mg Si ? Mg Si Fe Cu ? Sensitiv layer : ca µm eliminated AA 6060/6063 with normal % of elements Conversion coating chemical pure, if perfect etched !