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Deposizione rame su tubi in alluminio

Deposizione rame su tubi in alluminio - Forum Chimica

Deposizione rame su tubi in alluminio - Forum Scienza Chimica. Italian Chemistry Forum.


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  #1  
Old 01-06-2008, 03:43 PM
Max83
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Default Deposizione rame su tubi in alluminio



Salve a tutti,
vogliate scusarmi se magari ripropongo post gia trattati ma se vi
chiedo è perchè non ho trovato abbastanza, e in piu' perchè sono nuovo
di queste parti Beh vado al dunque:la mia domanda nasce da una mera
necessità pratica voglio brasare dei tubi in alluminio di piccolo
diametro 9mm con dei tubi in rame; ne nasce dunque la necessità di
ramare i tubi in alluminio per permetter la brasatura con lo
stagno.Ora quanto questo sia possibile non lo so, ma cmq facendo varie
prove ho ottenuto anke risultati decenti ma non riesco piu' a
ripeterli!!! ecco dunque vi chiedevo un po' tutto tipo: la
concentrazione del solfato di rame che tensione e che trattamenti
eseguire sul pezzo per ottimizzareil processo.
Grazie a tutti in anticipo e scusate se mi sono dilungato... Ciao!
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  #2  
Old 01-06-2008, 09:05 PM
Revenge
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Default Deposizione rame su tubi in alluminio

Sembra che Max83 abbia detto :


L'alluminio si può placcare ma devi pulire in modo adeguato e
particolare la superficie

Per la placcatura prova a fare prima lo strike come consigliato per le
sfere un paio di topic sotto
Potresti (dico potresti) tentare con la soluzione che ho fornito prima
a 50 grammi litro di solfato di rame
Se ci fossero problemi di eccessivo ribollimento suggerirei di stare a
pH più neutro (verso il 5-6) in modo da limitare gli effetti
dell'acido.
Non so se funziona quindi test and try.
Per rendere il rame meno efficace nell'autodeposizione ti conviene
portare il pH a 5-6 usando ammoniaca diluita che ben complessa il rame.
Poi puoi placcare come ho suggerito prima con la soluzione
solforico/soltato di rame e anodi in rame.

io poi sono disponibile per suggerimenti


QUANTO ALLA PULIZIA DELL'ALLUMINIO ESISTONO TOMI IN MATERIA quindi ti
ho trovato quanto sotto che dovrebbe darti indicazioni sufficienti.
Purtroppo è in inglese ma non credo per te sia un problema

leaning and Etching of Aluminum

Aluminum represents a special cleaning problem. The metal has high
reactivity; an oxide film of variable thickness is always present; and
many of the finishing processes for aluminum are sensitive to surface
residues. The cleaning formulations are therefore somewhat restricted,
and because of these restrictions, aluminum cleaners are generally
grouped as a special category. While it is quite true that cleaning
materials developed for aluminum will work quite well on other
substrates, the reverse is not always true.

Aluminum cleaners are subdivided into non-etch and etch types.

The non-etch types are generally used for processing buffed parts, or
parts made from prefinished or pre-rolled stock. They may also be
required prior to certain sensitive type coatings such as highly
corrosion resistant chromates.

The etch cleaners are used to produce matte finishes, and in particular
are widely used to produce finishes which mask surface imperfections
such as die marks, rolling imperfections, orange peel, score marks, and
other defects produced during, or as a result of, processing
procedures. Tonnage figures show the etch cleaners to be by far the
most widely used. Since etch cleaners are consumed in the process of
etching, an estimate of the comparative surface area processed in each
type of cleaner is not possible from this data. However, it does
indicate that etched finishes possibly predominate.

The non-etch cleaners fall into three general categories:

Acid,

Alkaline inhibited , and

Alkaline non-inhibited.

The acid cleaners are generally based on the fact that strong acids,
particularly oxidizing acids are capable of removing soils by chemical
breakdown of the soil. At the same time, the oxidizers present
passivate the surface of the aluminum. The non-oxidizing acid used must
have a relatively low rate of attack on aluminum and is generally
either phosphoric or sulfuric.

A typical formula would be:

85% Phosphoric acid 40 - 60% by volume

Nitric acid 20 - 30%

Water to make 100%

Temperature 38 - 72oC ( 100 - 160oF)

Sulfuric acid can often be substituted for phosphoric acid. Chromic
acid at a concentration of 60 - 180 g/L (8 to 24 oz/gal) can be
substituted for nitric acid, but because of the waste disposal problems
involved, this change may not be desirable. The use of chromic acid as
the oxidizing agent may be an important consideration ahead of the
application of certain chromate coatings, where it seems to improve the
corrosion resistance of the coating being applied.

The degree of surface attack can be controlled by the water content and
temperature to produce either a very light etch, or essentially no
attack at all. Buffed pieces passed through such a solution will often
suffer some slight loss of lustre, and develop a somewhat milky
appearance. This is apparently an optical effect due to the formation
of an oxide film. Plating with a bright nickel for example restores the
original buffed luster. In general, the use of such solutions is
limited to plating operations, partly because of the nature of the acid
solutions, and more importantly because of the appearance change noted.

The alkaline inhibited cleaners utilize the principle that alkaline
silicates will react with aluminum to form an insoluble aluminum
silicate. Silicates of various grades are incorporated in the cleaner
where they act as inhibitors by forming an insoluble silicate film on
the surface of the work. While this film is invisible, it is extremely
tenacious and continuous, and provides a barrier to further attack by
the solution. Chromates may be used in a similar manner, supplying the
oxidative power necessary to produce a continuous film of aluminum
oxide which inhibits further attack.

In either case, the protective film has a finite time of formation.
During this period, reaction of the surface with the solution occurs.
Thus, when the part is initially immersed, some gassing is evident.
This rapidly diminishes and stops however, and the resulting etch is
microscopic and essentially invisible. The slight gassing which does
occur helps to dislodge solid particles and speed cleaning.

Inhibited alkaline cleaners of this type can be formulated over a wide
range of composition. In general, they fall into two categories: pH 9.5
- 11.0, and pH over 11.0. The higher pH materials will develop heavier
inhibiting films with corresponding problems of removal later. They do
offer the advantage of being more effective on soils which can be
removed by saponification. The lower pH materials produce lighter
inhibiting films more easily removed and are particularly effective on
sulfurized oils. The time required for film formation is generally
considerably shorter with low pH materials and the microscopic etch
during the induction period is correspondingly reduced.

A typical low pH formula would be in the range of

Sodium bicarbonate 10 - 30%

Sodium silicate 30 - 50%

Complex phosphate 15 - 30%

Complexers 0 - 10%

Wetting agents 1 - 5 %

This formula is obviously more complicated than many of the older
formulations listed by Springer; Wernick and Pinner; and others. The
components are selected not only for their buffering capacity, but also
for their deflocculating and soil suspension characteristics. Where
local restrictions on phosphates still exist, it may be necessary to
eliminate these important constituents. Generally, they are replaced by
a combination of additional buffers, complexers such as EDTA and its
homologues, and deflocculants such as ligno sulfonates, resin
condensates, or condensed tall oil surfactants, making the formulas
still more complex. These non-etch cleaners will generally be operated
in the range of 30 - 90 g/l (4 to 12 oz/gal) and from 60 - 90 C (140 -
180 F). Time of immersion will depend on the soil to be removed but is
usually in the range of 2 to 10 minutes.

More recent developments have produced cleaners which operate at
considerably lower temperatures and concentrations - as low as 38oC
(100oF) and 15 to 30 g/L (2 - 4 oz/gal. The alkaline blend and balance
in these materials is similar to the standard compounds but the
surfactant blend is considerably altered. Displacement types are
generally operated at the lower temperatures and concentrations. Where
there is a limit on the hexane soluble content of the effluent, the
displacement types are preferred. The permit the removal of the
displaced oil by suitable grease traps. The removed oil can frequently
be reused or beneficially burned. All of these materials require that
the oil to be removed must be in the liquid state. Therefore the lowest
operating temperature possible is that at which all the components of
the oil are liquid. The incorporation of a 49oC (120oF) melt paraffin
in a forming oil would require an operating temperature of at least
54oC (130oF). Because of the high melting point of buffing compounds,
low temperature compounds are not usually suitable for buffing compound
removal.

As previously indicated, the inhibiting action used in this type of
cleaner is dependent on the formation of a film of aluminum silicate.
Unless the preliminary cleaning is to be followed by an etching
procedure, it is necessary to remove this film in a deoxidizing
solution before further processing. Such solutions consist of suitable
acid mixtures augmented with a controlled percentage of fluoride ion.

These deoxidizing solutions are often referred to as "desmutters" since
the also remove the smut formed by the segregated metals found in the
alloys and left behind after the removal of even small amounts of
aluminum by the alkaline cleaner.

A typical deoxidizing solution would be:

42 Be' Nitric acid 50 - 75% by vol

Fluoride salt 15 to 120 g/L (2 - 16 oz/gal)

For alloys containing appreciable percentages of magnesium, the
addition of sulfuric acid may be required:

42 Be' Nitric acid 50 - 75% by vol

Conc. Sulfuric acid 10 to 20%

Water to make 100%

Fluoride salt 15 - 120 g/L (2 - 16 oz/gal)

A mixture of this type is sometimes referred to as a "universal" acid
because it is suitable for all alloys.

The activity of the deoxidizing bath is to a large extent controlled by
the concentrations of nitric acid and fluoride salt. High
concentrations of readily available fluoride ion gives baths with very
high activity. For baths of this type, ammonium bifluoride is the
preferred source of fluoride. For slightly lower activity with an
appreciable reservoir of fluoride, potassium or sodium fluoride may be
used. And for low activity, silicofluoride, fluoborate, or another
slightly ionized complex fluoride may be used.

Mixtures based on chromic acid, chromic-sulfuric, sulfuric acid
hydrogen peroxide, and sulfuric acid with iron salts are also
available. Many of these combinations are formulated as dry powdered
acid salt mixtures by using hexavalent chromium salts, peroxygen salts,
or iron salts. When iron is used as the oxidizer, the concentration of
fluoride that can be added is quite limited since with will complex the
available iron and prevent it from acting as a protective oxidizer for
the aluminum.

The peroxygen desmutters tend to be unstable and have relatively short
life in the presence of certain catalysts such as copper and silver.
Special maintenance procedures must be followed if the alloys being
processed contain these metals. Recent work on the stabilization of
hydrogen peroxide has resulted in at least one grade that is suitable
for use in desmutting and deoxidizing solutions to replace the
peroxygen salts.

As previously mentioned, some processes such as chemical polishing and
certain chromating solutions are particularly susceptible to the
presence of silicate films remaining after the used of inhibited
alkaline cleaners. For these operations a deoxidizer operated to
provide complete removal of the silicate film would result in
noticeable etching of the surface. If such an etch cannot be tolerated,
consideration must be given to the use of the so-called non-silicated,
non-etch cleaners.

Non-silicated, Non-etch Aluminum Cleaners

These compounds are not in the strictest sense truly non-etching. They
are carefully buffered, mild etchants operated under controlled
conditions to hold the etch to a microscopic level. A typical mixture
would contain:

Alkali buffer mix for pH 9.0 90%

Complexers and deflocculants 5%

Wetting agents 5%

Occasionally, additional insurance against noticeable attack will be
provided by alkaline chromates. However, this practice is somewhat
dangerous since improper balance (sometimes resulting from aging of the
solution) can result in the development of an appreciable oxide coating
similar to that produced by the Alroc process. Waste disposal
conditions also limit this approach.

These solutions are usually operated in the range of 23 - 60 g/l (3 - 8
oz/gal) at 60 - 62oC (140 - 180oF). At the lower concentrations and
temperatures the etch will be essentially unnoticeable. Under the more
severe conditions, a definite "frosting" will usually occur, although
the etch will not be so severe that it cannot be eliminated by chemical
polishing or a bright plating operation. Careful attention to
operational conditions is a must with these solutions. Exceeding the
upper limits of concentration and temperature will result in excessive
etching. Falling below the lower limit can result not only in the
possibility of poor cleaning, but the possible development of a film of
undissolved aluminum salts on the surface.

While these cleaners, properly operated will leave the surface
generally free from any film, it is common practice to follow their use
with a simple nitric acid deoxidizing step - 25 - 75% by vol 42 deg Be'
nitric acid - to insure the removal of any trace of alloying elements
from the surface.

These cleaners may also be formulated for low temperature operation
with the same limitations previously mentioned. There is the further
advantage, that at the lower temperature, chemical attack is even more
limited.

Etching Cleaners

Etching cleaners for aluminum are based on the rapid reaction of
aluminum with alkalies according to the reaction:

1. 2 Al + 2 OH- + 4 H2O ---> 2 H2AlO3- + 3 H2

and

2. Al (OH)3 << ----->> H+ + H2AlO3 - which can also be written as

Al(OH)3 << ----- >> H+ + AlO2- + H2O

Additional alkali leads to

3. Al(OH)3 + 3 NaOH ------> Na3AlO2 + 3 H2O

and

4. Al(OH)3 + NaOH ------> NaAlO2 + 2H2O or NaAl(OH)4

The fact that sodium aluminate can be precipitated only from
concentrated solutions as well as the wide variety of forms in which it
appears, suggest the possibility that, at least in dilute solution, it
is not a true compound but a peptized hydroxide, or a colloidal
dispersion of the hydroxide. Furthermore, freshly precipitated material
is gelatinous and very absorptive, both characteristics of the
hydroxide. Sodium aluminate solutions also show abnormal viscosity.
This fact can explain many of the problems encountered with etching
baths.

The earliest etching solutions for aluminum consisted of sodium
hydroxide, occasionally modified with other alkalies. Maintaining a
uniform etch with these solutions was a difficult proposition.
Similarly, the baths would orm heavy deposits on coils, tank bottoms,
etc. which had to be removed by brute force.

In the early 1950's several patents were issued on additives,
principally sugar acids such as gluconic and glucoheptonic acids, for
the prevention of tank scaling and operation of the solutions became
somewhat easier. At the same time that the scaling problem was
overcome, it was noted that the etching action became more uniform, and
etching rates increased. In addition, gas tracking (the production of
etched grooves in parts as a result of gas following a fixed path along
the part to the surface) was almost eliminated, and rinsing was
simplified.

In extensive unpublished research at the time, the author noted that
not only acids, but the corresponding primary and secondary amines, as
well as some of the simple sugars in some cases, were effective for
this purpose. While it was generally noted that effective scale
prevention materials were capable of forming complexes, or chelate
links, with aluminum, the stability constant of the complex could not
be too high or the material would not perform well. Additionally, the
materials had to be highly hydroxylated and exhibit effective
performance in other applications where the deflocculating action was
the determining factor. From this data, it was concluded that a
possible function of these materials was a deflocculating action. If we
examine reactions 2 and 3 above, it is readily noted that to prevent
formation of the aluminum hydroxide, massive amounts of alkali are
required. However, if the reaction is not prevented, but the
precipitated hydroxide is deflocculated or peptized sufficiently, it
will not adhere to the aluminum surface to cause non-uniform etching,
nor to the tank walls to cause caking, but will undergo the
transformation

2 Al(OH)3 ---> Al2O3H2O + 2 H2O

in the body of the solution resulting in a granular precipitate easily
flushed from the tank. The additional deflocculating action also tends
to reduce the viscosity previously noted accounting thereby for the
elimination of gas tracking.

It was quickly noted that even with this type of solution, production
of specific etch patterns required modification and control. It became
common practice for example to discard only part of the etching
solution at a time since freshly made baths initially produced brighter
etches and required "aging" by dissolving some aluminum before reaching
a stable condition. The presence of other alkalies such as carbonate,
or phosphate could influence the appearance of the etch. In one
particular case where a highly characteristic etch pattern had to be
maintained with unusual uniformity, success was attained only by
frequent analysis and close control of 1. free alkalinity, 2. carbonate
concentration, 3. complexer concentration, and 4. concentration of
dissolved aluminum.

Where the etching solutions were used to dissolve aluminum mandrels
from electroformed parts, the rates were quickly be pushed to the point
where the gas involved in the reaction limited the access of the
solution to the interface and therefore limited the rates obtainable.
Oxidizers such as chlorate, chlorite, mixed nitrate/nitrite etc. were
added and still higher rates were obtained since the oxidizer reduced
hydrogen evolution and allowed better contact of the solution with the
surface. It was also noticed in this work that the oxidizer had a
pronounced effect on the appearance of the etch - in some cases
producing a more matte finish; in others, brightening almost in the
manner of a chemical polishing bath. Stock removal however was far too
high to allow such baths to be used for either purpose.

In general, etching solutions of this type are relatively poor
cleaners. The amount of gas evolved limits the amount and type of
surfactant which can be employed without developing excessive foaming.
This is particularly true since the finely divided aluminum hydroxide
present stabilizes foam readily.causing foam problems even with the
so-called non-foaming surfactants and even in the absence of surfactant
materials. Additionally, they are operated at relatively high pH and
therefore give poor performance on many soils such as sulfonated oils.
Variable etch patterns delineating the oil distribution can occur
easily.

It is common practice therefore to preclean critical parts in a
non-etch cleaner prior to etching. The non-silicated materials are
preferred for this purpose since they offer no possibility of
subsequent non-uniform etching as a result of adsorbed silicate.

All of these etching solutions have relatively high rates of attack and
leave the surface covered with a "smut" consisting of undissolved
alloying elements. The degree of smut formation naturally varies with
the alloy, and the depth of etch - from barely discernable to heavy
black - but can be removed in one of the acid deoxidizers previously
described.

With these formulations, one particular form of non-uniform etching
known as "spangling" still occurred periodically, particularly with
extruded alloys. One patent attributes this to the presence of
dissolved zinc in the etching solution and controls the problem with a
special additive to maintain the zinc concentration below a critical
level. As a corrollary advantage, it is claimed that the bath is free
from caking and never has to be discarded. In observing operational
baths it is noted that the baths show a rapid and marked increase in
viscosity as aluminum is dissolved, with a corresponding increase in
dragout. It is possible that the additive, in addition to controlling
the zinc, in some way stabilizes the aluminum in the NaAlO{2} form
accounting for the increased viscosity. The dragout might then
stabilize the aluminum content at a level below the precipitation point
preventing caking. The point has not been resolved. Considerable
amounts of precipitated hydroxide are visible in the rinse, however, so
the stabilization is apparently reversible on dilution. Very similar
results can be obtained by the addition of small amounts of sodium
sulfide to the etching solution instead of the proprietary addition
agent.

Acid Etching

One particularly fine etch with remarkable defect hiding power is an
acid etch using a fluoride acid salt at slightly elevated temperature.
The etch produced is extremely fine, non-reflective and uniform. Stock
removal is very low. Hiding power is exceptional.

The etch uses ammonium bi-fluoride at concentrations of 15 - 60 g/L (2
- 8 oz/gal) at temperatures from 20 to about 38 - 48oC (70 to about 100
- 120oF.).

Variations on this etch can be produced by modifying the fluoride with
other powdered acids to vary the attack rate. Sodium bisulfate,
sulfamic acid, and citric acid are among the acids that have been used.
Nitric acid or oxidizers must be avoided however since these act as
inhibiters and prevent the proper operation of the etch.

All etched finishes regardless of the method of development are
extremely susceptible to finger marking and staining unless protected
by an auxiliary coating of wax or clear coating of some type. Great
care has to be used in drying and handling prior to application of the
finish coating to avoid problems from this source.


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  #3  
Old 01-07-2008, 11:31 AM
Max83
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Default Deposizione rame su tubi in alluminio

Oh bene allora ti ringrazio prima di tutto!
ti espongo un pò di perplessità/difficoltà

allora ti dico subito che per quanto riguarda i materiali sono un pò
messo male purtroppo ho accesso solo a soluzioni da supermercato ossia
comeune acido muriatico soda caustica e ammoniaca ( al piu candeggiana
che dubito possa tornar utile) non riesco a reperire nemmeno l'acido
solforico ...mannaggia nemmeno na batteria al piombo!! quindi sto un
pò messo male per quanto riguarda anke la preparazione della
superficie




gia qui ti dico pulita la superficie alla meno peggio sgrassata con
comune sapone e lavaggio in acido muriatico (cosa probabilmente
sbagliata) e poi a bagno in una soluzione a 30g/l di solfato di rame
(cosa che assomiglia allo strike che hai descritto) crea gia
ribollimenti sulla superficie e il deposito che si crea è spugnoso con
un colpo di straccio se ne va proprio del tutto senza lasciare
traccia!

e gia qui non ho strumenti per la misura del Ph mi dovresti dare una
dritta!


managgia sapevo che l'alluminio era un pò particolare ma qui si fà
dura non ce le ho mica tutte quelle sostanze e nemmeno le
conoscenze...altro che dritta qui mi devi proprio dare uno spassionato
quanto pratico consiglio a modi guida dalla a alla z!

mi sa che mi devi proprio fare una ricetta su misura. Ah altra
curiosità: i modesti risultati che io ho ottenuto praticamente per
caso erano possibili solo se attuavo una agitazione esasperata del
pezzo di alluminio nella soluzione, cosa che non potrei permettermi
nel lavoro che devo fare; quindi mi domando è possibile fare la
deposizione tenedo la soluzione e i pezzi fermi!


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Old 01-07-2008, 01:10 PM
ziP
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Default Deposizione rame su tubi in alluminio


"Max83" <[Only registered users see links. ]> ha scritto nel messaggio
news:[Only registered users see links. ]...
non riesco a reperire nemmeno l'acido
solforico ...mannaggia nemmeno na batteria al piombo!! quindi sto un
pò messo male per quanto riguarda anke la preparazione della
superficie

Per l'acido solforico prova a cercare
in ferramenta o simili un disgorgante
per scarichi denominato "Disgorgante
idraulico" della ditta SAI spa di Roccabianca PR
contiene H2SO4 al 96%
ciao a tutti.
Paolo


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  #5  
Old 01-08-2008, 08:26 PM
Revenge
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Default Deposizione rame su tubi in alluminio

Max83 ha detto questo lunedì :
L'ACIDO SOLFORICO SI TROVA IN NEGOZIO FACILMENTE AL 93-96% SERVE PER
SGORGARE I CESSI.
INFATTI E' QUELLO IL GROSSO PROBLEMA DI ADESIONE DEL RAME SUGGERIREI
VISTE LE SCARSE RISORSE DI FARE UN TENTATIVO DI ALCALINIZZARE IL RAME
FINO AL PUNTO IN CUI NON DEPOSITA PIU' DA SOLO CON AMMONIACA, QUI NON
SERVONO STRUMENTI DI MISURA E UNA VOLTA CHE NON DEPOSITA PIU' PROVARE A
FARLO DEPOSITARE A BASSA DENSITA' DI CORRENTE (OVVERO CON BASSO
VOLTAGGIO QUI DIPENDE DA DOVE SI TROVA L'ANODO E CHE DISTANZA HA DAL
CATODO, MA DIREI A NASO CHE 4 VOLT DOVREBBERO ESSERE SUFFICIENTI PER UN
DEPOSITO LEGGERO)



COME SOPRA


DIREI CHE PER COMINCIARE PULIRLO CON UN PO DI ACQUA SAPONATA CON UN
POCHINA (MA MOLTO POCA SODA CAUSTICA) A CALDO (70-90°c) E POI LAVARLO
CON ACQUA DISTILLATA BENE PIU' VOLTE E POI DECAPARLO CON ACIDO
MURIATICO AL 5% POTREBBE ESSERE UN INIZIO, TI SUGGERIREI DI TAGLIARE UN
PEZZETTO DI TUBO E FARE DELLE PROVE IN PICCOLO PRIMA DI SCATENARTI
INDUSTRIALMENTE


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  #6  
Old 01-09-2008, 10:14 AM
Max83
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Default Deposizione rame su tubi in alluminio

On 8 Gen, 21:26, Revenge <[Only registered users see links. ]> wrote:


si ok sono andato da un'autoricambi e alla fine me ne ha dato un pò
(caro ma insomma) e al 36%
ho trovato anke soda caustica (solida a granelli) e ammoniaca...ma è
quela profumata per la casacomposizione tra il 5-15% si insomma non è
na meraviglia ma adesso ho quasi tutto!


cioè intendi aggiungo ammoniaca finche vedo che il rame non si
deposita piu sul pezzo alluminio che è da solo dentro la soluzione? e
poi comincio con la deposizione elettrochimica! ok se mi confermi io
intanto ci provo!


ecco temo un pò la reattività dell'allumino sia con sostanze basiche
sia acide.... si insomma bolle dentro a ste sostanze di solito vabbè
ci vado leggero con le concentrazioni!
Ti faccio sapere, tu dammi conferma!
grazie ankora ciao!

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  #7  
Old 01-09-2008, 01:20 PM
Max83
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Default Deposizione rame su tubi in alluminio

ehm ho fatto una prova con 0,1 l di soluz di solfato di rame a 50g/l e
ho aggiunto 1ml ammoniaca come dicevo prima diluita al 5-15% la
soluzione è diventata torbida ed opaca con un colore piu chiaro sembra
quasi che sedimenti ..anzi forse lo fa ho messo il tubetto circa 0.5A/
dm2 facendo i conti (solo della sup. ext. del tubo quindi al limite è
metà) e il risultato è pessimo si attaca in modo disomogeneo lo strato
è poroso anzi direi polverulento e sopratutto non ha adesione!
Aiutooo!
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  #8  
Old 01-09-2008, 01:22 PM
Max83
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Default Deposizione rame su tubi in alluminio

scusate mi sono sbagliato......
erano 5ml di ammoniaca! 1ml è la prova che sto facendo ora!
Ciao!

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  #9  
Old 01-09-2008, 02:21 PM
Soviet_Mario
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Default Deposizione rame su tubi in alluminio

Max83 ha scritto:

è una concentrazione piuttosto insolita per l'acido solforico
commerciale ... c'è scritto chiaramente sull'etichetta che è
proprio tale ? Te lo chiedo perché è spesso la concentrazione
con cui vendono HCl concentrato e non H2SO4. Se non ha etichetta
e/o se aperta fuma all'aria, è come dico io. Se no, e spero
così, allora OK. Se la bottiglia ti sembra pesare circa il
doppio del dovuto, potrebbe essere il 96 % scritto poco
leggibile ... Ho questo sospetto perché non ricordo se nelle
batterie da auto si vende così diluito (mi pare che fosse più
concentrato di così, nel qual caso non sarebbe possibile usarlo
a tale scopo, e allora a che cavolo servirebbe ?). Anche in
enologia lo trovi : acido per pulizia delle botti di plastica o
vetroresina dalle incrostazioni tartarico-tanniche.


ai megastore meno cari (discount vari, LIDL etc) le versioni
base non profumate e non addittivate (oltre lo stretto
essenziale, tipo con stabilizzanti se servono) di ammoniaca,
candeggina, alcool (ha i denaturanti), si trovano sempre, basta
cercare, e guardare il prezzo (che è il minore di solito, e la
marca pure è senza nome ossia da filiera e ridenominata con la
firma della catena stessa di distribuzione, o cmq della line adi
prodotti bundle. Bennet ad esempio ridenomina i prodotti non
firmati di cui si fa garante, diciamo, Lidl ha altre filiere
spesso germaniche). Cmq sia i prodotti base ci sono sempre nei
megastore. Data l'applicazione (e dato anche che costano meno),
sono imho consigliabili in genere, salvo constatare che magari
addittivi tensioattivi nelle elettrolisi male spesso non fanno e
anzi sono di aiuto. Ma anche li, meglio addittivare a parte e
sapere cosa usi e quanto ne usi.

acetone "puro" di grado tecnico (non male) invece lo dovresti
trovare dai BRICO


no, voleva dirti di preparare a parte (separatamente) una
soluzione di complesso (blu notte) di diammino rame solubile,
che è piuttosto diluita dato che alcalinizzando parte rilevante
del rame, se non si prendono precauzioni, precipita come
idrossido bluazzurro gelatinoso, o se a caldo come ossido
marrone nerastro. I precipitati vanno filtrati, e qual che resta
è il diammino rame, diluito, solubile anche a piacchi basici.
Questo è un grosso pregio, perché nelle scariche catodiche
spesso si creano ambienti alcalini, che in assenza del complesso
possono precipitare il rame idrossido gelatinoso o l'ossido,
magari coprecipitandoli con la placcatura, o cmq facendola
venire peggio. Altri pregi sono la maggiore lentezza di scarica
del rame complesso, che non ha più una grossa tendenza alla
deposizione diretta e incontrollata per scambio rame/alluminio
tipica del cloruro (e meno del solfato) di rame acidi. Inoltre
anche la scarica dell'idrogeno gassoso, che dal punto di vista
della compattezza delle placcature è spesso nociva e rende più
porosi gli strati, è fortemente limitata a piacchi basici.
Il processo è più lento con diammino rame, ma la lentezza
(chiedo conferma) potrebbe essere un pregio, portando a
ricoperture più affinate e compatte.

Cmq l'alluminio lo aggiungi solo dopo avere preparato la
soluzione bluviola scura di diammino rame II, e non vedrai quasi
un accidente di cosa succede dentro, senza tirare fuori il
pezzo. LEgalo in anticipo con una cordicella


anche i tempi regolali di conseguenza. Se l'attacco, magari a
caldo, è potente, i tempi di pulizia vanno accorciati

ciao
Soviet

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  #10  
Old 01-09-2008, 10:31 PM
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Default Deposizione rame su tubi in alluminio

Scriveva Soviet_Mario mercoledì, 09/01/2008:

Presumo che i profumanti dell'ammoniaca siano precipitati, soviet come
sempre ha centrato il problema nel senso che il complesso diamminorame
placca più lentamente (infatti si usano densità di corrente basse) che
permettono di dare il primo strato alla nostra tubazione. Poi si placca
realmente con una soluzione solforico/solfato di rame standard sopra
questo straterello aderente.
CApisco che con mezzi di fortuna è difficile placcare, se riesce ok se
no ho la soluzione alternativa che è più laboriosa ma da risultati
diciiamo accettabili.


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