CN101265601A
Title: Aluminium alloy surface electric plating iron machining process
Abstract: A process for galvanizing iron on an aluminum alloy surface includes the following steps: (1)
glaring, an aluminum alloy galvanized component is provided and carries out glaring treatment; (2)
washing, the galvanized component after glaring treatment is washed; (3) zincing, the galvanized
component after washing carries out zinc impregnation; (4) galvanizing, a plating bath is provided,
electroplating solution mixed by ferrous chloride of 350g/L, sodium chloride of 10g/L, manganese
chloride of 3g/L and boric acid of 5g/L is added into the plating bath, the pH value of the electroplating
solution is 1.2, the galvanized component is put in the plating bath and carries out electrolytic reaction
for 8 min at the temperature of 45 DEG C, the current density is 4A/dm<2>; (5) neutralizing the
electroplating solution, the galvanized component after galvanization carries out the treatment of
neutralizing the electroplating solution; (6) the galvanized component carries out rust-proofing
treatment and natural airing to obtain a finished product. The plating formed on the surface of the
aluminum alloy galvanized component has even thickness and glaring appearance, and mass production
can be realized.
Description:
Technical field
The invention relates to a plating solution, a plating solution used therein, in particular to a process for
electroplating iron on the surface of an aluminum alloy.
technical background
Electroplating is the use of electrolysis to deposit a well-attached metal coating on a mechanical
product, but the properties are different from the base material. Generally, it is decorative on the
mechanical product and has various functional surface layers. It can also repair wear. And machining
errors in the workpiece. At present, in the processing technology of electroplating iron on the surface of
aluminum alloy, the thickness of the iron plating layer is not uniform, the surface of the plating layer is
rough, and the final processing precision cannot be met. Therefore, after electroplating iron processing
on the surface of the aluminum alloy, electroplating is also required. The parts are machined to meet
the requirements of high precision, and the processing steps are complicated. Moreover, the plating
thickness of the plated parts cannot be consistent at each plating, and the requirements for mass
production cannot be achieved.
Summary of the invention
The technical problem to be solved by the present invention is to provide a processing technology for
forming an iron-plated surface of an aluminum alloy surface which can form a uniform coating thickness
on the surface of the plating member, and the surface of the plating layer is bright, and the processing
precision can be achieved by electroplating.
The present invention has been achieved by the following means.
The principle of electroplating iron on aluminum alloy surface, the main point is that it includes the
following sequential steps:
1、Light-emitting, providing an aluminum alloy plating part, and performing electroplating processing
on the electroplated parts;
2、After washing with water, the plated parts after the light treatment are washed with water;
3、Dipping zinc, immersing the plated parts after washing;
4、Electroplating, providing a plating tank, adding 350-400 g/L of ferrous chloride, 10-20 g/L of sodium
chloride, 1-5 g/L of manganese chloride and 5-8 g/L of boric acid in the plating tank The plating solution,
the plating solution has a pH of 1.2 to 1.6, and the electroplating member is placed in a plating bath, and
the electrolysis reaction is carried out for 8 to 10 minutes at a temperature of 45 ° C to 55 ° C and a
current density of 4 to 10 A/dm 2 ;
5、Neutralizing the plating solution, and performing electroplating solution treatment on the
electroplated parts after electroplating;
6、The plated parts are rust-proofed and dried naturally to obtain the finished product.
In this way, the aluminum alloy plating part is subjected to light treatment before electroplating, the
purpose of which is to further remove the defects of the aluminum surface, and remove various alloying
elements and inclusions from the surface of the aluminum alloy to form a uniform aluminum-rich
surface, which is the latter The process provides a good substrate. The aluminum has elements such as
copper, magnesium, silicon, manganese and zinc. If it is not removed, it cannot be directly plated on
these alloy components, and it is easy to cause poor bonding or pinholes.
On the surface of the aluminum, there is a natural dense oxide film having a thickness of about 5 to 20
nm. Without removing it, it is difficult to obtain a plating layer having a good bonding force. The purpose
of zinc immersion is to remove the oxide film on the one hand, and to form a replacement layer of zinc
on the surface of the aluminum, which acts as a barrier to isolate the surface from which the oxide film
is removed from the atmosphere and from oxidation.
After the light-emitting and immersion treatment, the plating part is placed in an electrolytic bath for
electroplating, the composition and content of the plating solution in the electrolytic bath, and the
influence of plating temperature and current density on the plating layer:
The effect of ferrous chloride concentration:
The concentration of ferrous chloride is closely related to the plating rate. The concentration is high, the
plating speed is fast, the concentration is low, and the plating speed is slow. However, if the
concentration is too high, the required temperature needs to be increased accordingly. Otherwise, the
brittleness of the coating increases, which is not conducive to improving the primary plating. The thick
capacity, at the same time due to the increase of temperature, the evaporation of the solution is
increased, the impact on the equipment and the environment is increased, so the medium
concentration of the plating solution, that is, ferrous chloride is 350g / L ~ 400g / L.
The effect of boric acid concentration:
Boric acid in the plating solution plays a crucial role in the stabilization of the pH during electroplating
Table 1 Effect of boric acid content on pH value change
The analysis results show that with the increase of boric acid content in the plating solution, the amount
of hydrochloric acid required to change the pH value of the plating solution has a significant increase,
but when the boric acid exceeds 8, the trend begins to become smaller, so the stability from the plating
solution The economical consideration is to select a boric acid content of 5g/L to 8g/L.
The effect of manganese chloride concentration:
The addition of manganese chloride can refine the crystal grains, make the coating layer fine and
uniform, reduce the internal stress of the coating layer, and improve the ability of one-time plating
thickness. However, if the content is too much, the brittleness of the coating layer will increase, so the
content is controlled at 1g/L~ 5g / L is appropriate.
The effect of sodium chloride concentration:
Sodium chloride is added to increase the conductivity of the solution. As the content increases, the
brittleness of the coating increases. Therefore, it should not be excessively added and controlled
between 10g/L and 20g/L.
The impact of PH:
PH has a significant effect on the appearance of the coating and current efficiency (coating thickness
under the same conditions)
Table 2 PH value on the appearance of coating and current efficiency
Plating conditions: current 10A/dm2, 50°C, 10 minutes
Effect of temperature on the coating:
The temperature is low, the stress of the coating is large, the coating is prone to brittle shedding, the
temperature is high, the corrosion of the solution is strengthened, and the dissolution of the zincimpregnated layer is accelerated, which is also unfavorable for the adhesion of the coating (foaming of
the coating), so we strictly control 45 ° C ~ 55 ° C.
The effect of current density:
Current density has a significant effect on the appearance of the coating, ring groove size and plating
speed
Table 3 Effect of current density on coating appearance, ring groove size and plating speed
Plating conditions: pH 1.5, 50 ° C, 10 minutes
From the results, it can be analyzed that when the current density is too small, the plating rate is
significantly reduced, which is not conducive to the control of production cost. When the current density
is too large, the coating has obvious tip discharge phenomenon and even partial scorch.
After electroplating, there is residual acid plating solution on the surface of the electroplated part and
inside the substrate. If it is not cleaned, it will cause corrosion to the plating part and the plating layer,
so it is neutralized with an alkaline solution. The pure iron coating will soon corrode and rust in the air.
In order to better protect the coating, it will be rust-proof after plating, and dried naturally to obtain the
finished product.
Therefore, after the above-mentioned aluminum alloy surface electroplating iron processing process,
the thickness of the plating layer is uniform on the surface of the aluminum alloy plated part, the plating
layer is bright, and mass production can be realized.
The invention can be further specifically:
The light output includes the following steps:
1、Providing a pickling tank, adding a mixed solution of 750-850 ml/L of nitric acid and 150-250 ml/L of
hydrofluoric acid in the pickling tank;
2、The plated part is placed in a pickling tank and reacted at room temperature for 10 to 30 seconds.
The light can be washed with alkali or pickled. Generally, the corrosion of aluminum is small by pickling,
which not only ensures the surface finish and dimensional tolerance, but also because the alloy
elements are removed more thoroughly, the bonding strength of the obtained coating is relatively high.
Therefore, the pickling pair is selected. The plated parts are subjected to light treatment.
It must be thoroughly washed with water between each step to avoid the residual liquid from the
previous process being brought into the next process, so:
The water washing after the light discharge includes 1 to 3 times of flowing water washing, and the
plated parts are placed in a countercurrent rinsing tank, and washed with tap water at room
temperature.
The zinc immersion comprises the following sequential steps:
1、Zinc immersion, providing a zinc dipping tank, adding 400-500 g/L sodium hydroxide, 80-100 g/L zinc
oxide, 5-10 g/L sodium potassium tartrate and 0-3 g/ in a zinc dipping tank. a mixed solution of L ferric
chloride, the plating part is placed in a zinc dipping tank, and reacted at room temperature for 40 to 60
seconds;
2、Washing, electroplating the plated parts 1 to 3 times, providing a countercurrent rinsing tank,
placing the plated parts in a countercurrent rinsing tank, and washing with tap water at room
temperature;
3、Dezincification, providing an acid tank, adding a 1:1:1 mixed solution of nitric acid and water in an
acid tank, and placing the electroplated parts in an acid tank to react at room temperature for 10 to 60
seconds;
4、Zinc-dip two, providing a zinc dipping tank, adding 100-150 g/L sodium hydroxide, 20-40 g/L zinc
oxide, 5-10 g/L sodium potassium tartrate and 0-3 g/ in the zinc dipping tank. a mixed solution of L ferric
chloride, the plating part is placed in a zinc dipping tank, and reacted at room temperature for 20 to 40
seconds;
5、After washing, the plated parts are washed by water for 1 to 3 times, and a countercurrent rinsing
tank is provided. The plated parts are placed in a countercurrent rinsing tank and washed with tap water
at room temperature.
The surface of the aluminum has a natural dense oxide film, and the thickness of the film is about 5 to
20 nm. Without removing it, it is difficult to obtain a plating layer having a good bonding force. The
purpose of zinc immersion is to remove the oxide film on the one hand, and to form a layer of zinc on
the surface of the aluminum, which acts as a barrier to prevent the surface of the oxide film from being
isolated from the atmosphere and protected from oxidation; The zinc layer obtained by sub-dip
galvanizing is generally rough and the coverage is incomplete. In order to obtain a zinc immersion layer
with a more uniform surface and better quality, the first zinc immersion layer is generally removed by
using a nitric acid having a volume ratio of 1:1; Retreat, further passivation of the aluminum matrix,
revealing a more uniform aluminum-rich surface, a second thinning, more uniform, more dense zincimpregnated layer, the second zinc-dip layer if the color is not found Even or spotted, need to be reextracted and then dipped.
The neutralizing plating solution includes the following sequential steps:
1、Washing, electroplating the plated parts 1 to 3 times, providing a countercurrent rinsing tank,
placing the plated parts in a countercurrent rinsing tank, and washing with tap water at room
temperature;
2、Neutralization, providing a water washing tank, adding 50-100g / L sodium bicarbonate solution in
the water washing tank, the flowing water washed plating parts are placed in a water washing tank and
neutralized at room temperature for 5-10 minutes;
3、Washing, electroplating the plated parts 1 to 3 times, providing a countercurrent rinsing tank,
placing the plated parts in a countercurrent rinsing tank, and washing with tap water at room
temperature;
After electroplating, there is residual acid plating solution on the surface of the electroplated part and
inside the substrate. If it is not cleaned, it will cause corrosion to the plating part and the plating layer,
so it is neutralized with an alkaline solution.
The anti-rust treatment includes the following sequential steps:
1、Blackening, providing a blackening tank, adding 50-70g/L sodium thiosulfate, 4-7g/L ammonia
chloride, 7-10ml/L nitric acid and 5-8ml/L in the blackening tank The phosphoric acid mixed solution, the
electroplating member is placed in a blackening tank and reacted at a temperature of 15 ° C to 30 ° C for
2 to 5 min;
2、Washing, electroplating the plated parts 1 to 3 times, providing a countercurrent rinsing tank,
placing the plated parts in a countercurrent rinsing tank, and washing with tap water at room
temperature;
3、Filling, providing a filling tank, adding 3% to 5% of soapy water in the filling tank, placing the plating
part in the filling tank, so that the plating part is immersed at a temperature of 85 ° C ~ 95 ° C for 3 ~ 5
min;
4、Washing, electroplating the plated parts 1 to 3 times, providing a countercurrent rinsing tank,
placing the plated parts in a countercurrent rinsing tank, and washing with tap water at room
temperature;
5、Hot water washing, providing a countercurrent rinsing tank, the plating part is placed in a
countercurrent rinsing tank, and washed at a temperature of 60 ° C ~ 80 ° C for 1-2 min;
6、Blow dry, use the air gun to dry the plated parts to the visually anhydrous;
7、Dip the rust-proof water, provide a washing tank, add anti-rust water to the washing tank, place the
plated parts in the washing tank, and soak for 1 to 2 minutes at room temperature.
The pure iron coating quickly erodes and rusts in the air. In order to better protect the plating layer,
blackening is performed after plating to form iron sulfide on the surface of the iron plating layer. The
iron sulfide layer does not completely prevent the occurrence of corrosion of the plating layer, so the
process of immersing the rust-proof water is increased after blackening.
Because the surface of the part may be contaminated with oil before processing, therefore;
Before the electroplating process, the degreasing process is further provided, and an ultrasonic cleaning
machine is provided. The cleaning agent is added into the cleaning tank of the ultrasonic cleaning
machine, and the electroplating parts are placed in the cleaning tank of the ultrasonic cleaning machine
to be cleaned and degreased.
Thus, the purpose of degreasing is to remove dirt on the surface of the part, rust preventive oil, and
substances that remain on the surface of the plated part in the previous process.
In summary, the present invention has the following advantages over the prior art: the processing
technology of electroplating iron on the surface of the aluminum alloy of the present invention forms a
uniform coating thickness on the surface of the aluminum alloy electroplating part, and the appearance
of the plating layer is bright, and can be directly achieved by electroplating processing. Processing
precision requirements, and can achieve mass production, widely used in the electroplating of various
aluminum alloy mechanical products.
Detailed ways
Best embodiment:
In this embodiment, the electroplating iron on the surface of the cast aluminum alloy piston is taken as
an example. The electroplating iron on the surface of the aluminum piston is required to have a plating
thickness of 6.5 μm to 33 μm on the working surface of the piston skirt, and meet the pre-plating:
groove groove width=1.6510+0.025, after plating: ring The groove width is ≥1.639; the coating is
uniform and dense, no burr; the adhesion of the coating can meet the thermal shock method or the grid
method is not allowed to fall off, the internal combustion engine bench test is 300 hours, and the plating
is not allowed to fall off; the corrosion resistance of the coating meets the wet heat test for 96 hours. No
rust. The aluminum piston electroplating process includes the following sequential steps:
1、Degreasing, an ultrasonic cleaning machine is provided, a cleaning agent is added in the cleaning
tank of the ultrasonic cleaning machine, and the aluminum piston is placed in the cleaning tank of the
ultrasonic cleaning machine to clean and remove the oil;
2、To provide light, a pickling tank is provided. A mixed solution of 800 ml/L of nitric acid and 200 ml/L
of hydrofluoric acid is added to the pickling tank, and the aluminum piston is placed in a pickling tank
and reacted at room temperature for 20 seconds.
3、Three times of water washing, providing a countercurrent rinsing tank, placing the aluminum piston
in a countercurrent rinsing tank, and washing with tap water at room temperature;
4、Zinc-dip, providing a zinc dipping tank, adding 500 g/L of sodium hydroxide, 100 g/L of zinc oxide, 10
g/L of sodium potassium tartrate and 3 g/L of ferric chloride in a zinc dipping tank Solution, the
aluminum piston is placed in a zinc dipping tank, and reacted at room temperature for 50 seconds;
5、Three times of water washing, providing a countercurrent rinsing tank, placing the aluminum piston
in a countercurrent rinsing tank, and washing with tap water at room temperature;
6、Dezincification, providing an acid tank, adding a 1:1:1 mixed solution of nitric acid and water in an
acid tank, and placing the aluminum piston in an acid tank to react at room temperature for 30 seconds;
7、Zinc-dip two, providing a zinc dipping tank, adding 150 g/L of sodium hydroxide, 40 g/L of zinc oxide,
10 g/L of sodium potassium tartrate and 3 g/L of ferric chloride in a zinc dipping tank Solution, the
aluminum piston is placed in a zinc dipping tank, and reacted at room temperature for 30 seconds;
8、Three times of water washing, providing a countercurrent rinsing tank, placing the aluminum piston
in a countercurrent rinsing tank, and washing with tap water at room temperature;
9、Electroplating, providing a plating tank, adding 350 g/L of ferrous chloride, 10 g/L of sodium chloride,
3 g/L of manganese chloride and 5 g/L of boric acid in a plating bath, and the pH of the plating solution
The value is 1.2, the aluminum piston is placed in the plating tank, and the electrolysis reaction is carried
out for 8 minutes at a temperature of 45 ° C and a current density of 4 A/dm 2 ;
10、Three times of water washing, providing a countercurrent rinsing tank, placing the aluminum piston
in a countercurrent rinsing tank, and washing with tap water at room temperature;
11、Neutralization, providing a water washing tank, adding 50 g / L sodium bicarbonate solution in a
water washing tank, placing the aluminum piston in a water washing tank and neutralizing the reaction
at room temperature for 10 min;
12、Three times of water washing, providing a countercurrent rinsing tank, placing the aluminum piston
in a countercurrent rinsing tank, and washing with tap water at room temperature;
13、Blackening, providing a blackening tank, adding 50g/L sodium thiosulfate, 4g/L ammonia chloride,
7ml/L nitric acid and 5ml/L phosphoric acid mixed solution in the black tank, the aluminum piston Placed
in a blackening tank at a temperature of 20 ° C for 3 min;
14、Three times of water washing, providing a countercurrent rinsing tank, placing the aluminum piston
in a countercurrent rinsing tank, and washing with tap water at room temperature;
15、Filling, providing a filling tank, adding 4% soapy water in the filling tank, placing the aluminum
piston in the filling tank, so that the aluminum piston is immersed at 85 ° C for 5 min;
16、Three times of water washing, providing a countercurrent rinsing tank, placing the aluminum piston
in a countercurrent rinsing tank, and washing with tap water at room temperature;
17、Hot water washing, providing a countercurrent rinsing tank, placing the aluminum piston in a
countercurrent rinsing tank, and washing at a temperature of 70 ° C for 2 min;
18、Blow dry, use the air gun to dry the plated parts to the visually anhydrous;
19、Dip anti-rust water, provide a washing tank, add anti-rust water in the washing tank, put the
aluminum piston into the washing tank, and soak for 2min at room temperature.
20、It is naturally dried to produce a finished product.
The parts not described in the present invention are the same as those in the prior art.
Claims
1.The processing technology for electroplating iron on the surface of an aluminum alloy is characterized
in that it comprises the following sequential steps:
1.1Light-emitting, providing an aluminum alloy plating part, and performing electroplating processing on
the electroplated parts;
1.2After washing with water, the plated parts after the light treatment are washed with water;
1.3Dipping zinc, immersing the plated parts after washing;
1.4Electroplating, providing a plating tank, adding 350-400 g/L of ferrous chloride, 10-20 g/L of sodium
chloride, 1~5 g/L of manganese chloride and 5-8 g/L of boric acid in the plating tank The plating solution,
the plating solution has a pH of 1.2 to 1.6, and the electroplating member is placed in a plating bath, and
the electrolysis reaction is carried out for 8 to 10 minutes at a temperature of 45 ° C to 55 ° C and a
current density of 4 to 10 A/dm 2 ;
1.5Neutralizing the plating solution, and neutralizing the electroplating solution by plating the
electroplated parts;
1.6The plated parts are rust-proofed and dried naturally to obtain the finished product.
2. The method for electroplating iron on an aluminum alloy surface according to claim 1, wherein the
light output comprises the following steps:
2.1Providing a pickling tank, adding a mixed solution of 750-850 ml/L of nitric acid and 150-250 ml/L of
hydrofluoric acid in an acid tank;
2.2The plated part is placed in a pickling tank and reacted at room temperature for 10 to 30 seconds.
3. The process for electroplating iron on the surface of an aluminum alloy according to claim 1, wherein
the water washing after the light extraction comprises 1 to 3 times of flowing water washing, and the
plated part is placed in a countercurrent rinsing tank and washed with tap water at room temperature.
4. The aluminum alloy surface electroplating process according to claim 1, wherein the zinc immersion
comprises the following sequential steps:
4.1Zinc immersion, providing a zinc dipping tank, adding 400-500 g/L sodium hydroxide, 80-100 g/L zinc
oxide, 5-10 g/L sodium potassium tartrate and 0-3 g/ in a zinc dipping tank. a mixed solution of L ferric
chloride, the plating part is placed in a zinc dipping tank, and reacted at room temperature for 40 to 60
seconds;
4.2Washing, electroplating the plated parts 1 to 3 times, providing a countercurrent rinsing tank, placing
the plated parts in a countercurrent rinsing tank, and washing with tap water at room temperature;
4.3Dezincification, providing an acid tank, adding a 1:1:1 mixed solution of nitric acid and water in an
acid tank, and placing the electroplated parts in an acid tank to react at room temperature for 10 to 60
seconds;
4.4Zinc-dip two, providing a zinc dipping tank, adding 100-150 g/L sodium hydroxide, 20-40 g/L zinc
oxide, 5-10 g/L sodium potassium tartrate and 0-3 g/ in the zinc dipping tank. a mixed solution of L ferric
chloride, the plating part is placed in a zinc dipping tank, and reacted at room temperature for 20 to 40
seconds;
4.5After washing, the plated parts are washed by water for 1 to 3 times, and a countercurrent rinsing
tank is provided. The plated parts are placed in a countercurrent rinsing tank and washed with tap water
at room temperature.
5. The aluminum alloy surface electroplating process according to claim 1, wherein the neutralizing
plating solution comprises the following sequential steps:
5.1Washing, electroplating the plated parts 1 to 3 times, providing a countercurrent rinsing tank, placing
the plated parts in a countercurrent rinsing tank, and washing with tap water at room temperature;
5.2Neutralization, providing a water washing tank, adding 50-100g / L sodium bicarbonate solution in
the water washing tank, the flowing water washed plating parts are placed in a water washing tank and
neutralized at room temperature for 5-10 minutes;
5.3After washing, the plated parts are washed by water for 1 to 3 times, and a countercurrent rinsing
tank is provided. The plated parts are placed in a countercurrent rinsing tank and washed with tap water
at room temperature.
6. The aluminum alloy surface electroplating process according to claim 1, wherein the anti-rust
treatment comprises the following sequential steps:
6.1Blackening, providing a blackening tank, adding 50-70g/L sodium thiosulfate, 4-7g/L ammonia
chloride, 7-10ml/L nitric acid and 5-8ml/L in the blackening tank The phosphoric acid mixed solution, the
electroplating member is placed in a blackening tank and reacted at a temperature of 15 ° C to 30 ° C for
2 to 5 min;
6.2Washing, electroplating the plated parts 1 to 3 times, providing a countercurrent rinsing tank, placing
the plated parts in a countercurrent rinsing tank, and washing with tap water at room temperature;
6.3Filling, providing a filling tank, adding 3% to 5% of soapy water in the filling tank, placing the plating
part in the filling tank, so that the plating part is immersed at a temperature of 85 ° C ~ 95 ° C for 3 ~ 5
min;
6.4Washing, electroplating the plated parts 1 to 3 times, providing a countercurrent rinsing tank, placing
the plated parts in a countercurrent rinsing tank, and washing with tap water at room temperature;
6.5The hot water is washed, and a washing tank is provided. The plated part is placed in a
countercurrent rinsing tank and washed with water at a temperature of 60 ° C to 80 ° C for 1 to 2 min.
6.6Blow dry, use the air gun to dry the plated parts to the visually anhydrous;
6.7Dip the rust-proof water, provide a washing tank, add anti-rust water to the washing tank, place the
plated parts in the washing tank, and soak for 1 to 2 minutes at room temperature.
7. The process for processing iron-plated iron on the surface of an aluminum alloy according to claim 1,
further comprising: removing oil before the electroplating process, providing an ultrasonic cleaning
machine, adding a cleaning agent to the cleaning tank of the ultrasonic cleaning machine, The plated
parts are placed in a cleaning tank of the ultrasonic cleaner to be cleaned and degreased.