JPH024997A - Production of copper in material for heat exchanger - Google Patents

Abstract

PURPOSE:To obtain a copper fin material having improved corrosion resistance without lowering heat conductivity by adding a specified amt. of a compd. such as Na2SO4, Al2(SO4)3 or H3BO3 to an Ni-Zn alloy plating soln. having a prescribed compsn., adjusting the pH of the resulting soln. and using the soln. as an electrolytic soln. CONSTITUTION:A plating soln. contg. 39-77g/l (expressed in terms of metallic Ni) water soluble Ni compd. and 6-68g/l (expressed in terms of metallic Zn) water soluble Zn compd. is prepd. One or more among 5-120g/l Na2SO4, 5-60g/l Al22(SO4)3.14-18H2O, 5-60g/l H3BO3, 3-15 g/l sodium naphthalenedisulfonate and 90-250g/l NH4Cl are added to the aq. soln. and dissolved. The pH of the resulting soln. is adjusted to 0.9-5.8 and the soln. is used as an electrolytic soln. A Cu (alloy) bar as the cathode is plated with a Zn-Ni alloy by electrolysis in the electrolytic soln. to produce a fin material for a heat exchanger. The thickness of this copper fin material can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a method for manufacturing a fin material for a copper heat exchanger, which is suitable for heat exchangers used in highly corrosive environments such as automobiles. This improves corrosion resistance and allows thinner fins without reducing conductivity.

[Prior art and problems to be solved by the invention] In recent years, as the weight of automobile heat exchangers has been reduced, there has been an increasing trend toward thinner fin materials for heat exchangers. In spraying areas and coastal areas, deterioration of heat dissipation characteristics due to severe corrosion and wear of fins due to chloride has become a problem.

In general, fin materials for heat exchangers are required to have not only corrosion resistance but also thermal conductivity, strength, etc. If the fin material itself is alloyed by adding a third element to give it corrosion resistance against salt corrosion, the thermal conductivity will be significantly reduced, making it unsuitable as a fin material for a heat exchanger. Therefore, there is a demand for a fin material for a heat exchanger that exhibits sufficient thermal conductivity even when made thinner, and also exhibits excellent corrosion resistance in harsh environments.

In such a situation, Z on the surface of the highly conductive Cu-based material
A fin material for a heat exchanger has been proposed in which a diffusion layer of n is formed to protect the internal core material as a sacrificial anode, and the core material has thermal conductivity. However, there is a problem in that Zn disappears due to dezincification corrosion peculiar to Zn alloys, and the sacrificial anode effect of Zn cannot be maintained for a long period of time. However, due to the thermal conductivity of the Zn diffusion layer formed on the surface layer,
If the dezincification corrosion of the Zn diffusion layer can be effectively suppressed and prevented, although it is limited to a few micrometers on one side, a fin material for heat exchangers with even better corrosion resistance can be expected, and thinner fins can be achieved.

Sb and As are elements that suppress dezincification corrosion peculiar to brass.
, P are known, but these can be coated with Cu-
It is relatively difficult to add Zn into the diffusion layer. Therefore, in order to add a third element effective for improving corrosion resistance into the Cu-Zn diffusion layer by wet plating, the above-mentioned sb etc.
It is necessary to perform n-X alloy plating to improve the corrosion resistance of the Zn diffusion layer itself. Various types of ZnX alloy plating can be considered. In particular, Zn-Ni alloy plating has long been known as an anomalous eutectoid alloy plating in which Zn, which is less noble in potential, precipitates preferentially, and is widely used in the steel industry. Although its application has been seen in some automobile steel sheets, it cannot necessarily be said that the technology is sufficiently established, and its application to copper-based materials is an unknown field.

[Means to solve the problem]

In view of this, as a result of various studies, the present invention has discovered a plating solution that can provide ZnNi alloy plating that is effective in reducing dezincification corrosion of the Zn diffusion layer formed on the surface of copper-based materials and improving corrosion resistance. As a result of further research, we developed a method for producing fin materials for copper-based heat exchangers that have excellent corrosion resistance.

That is, one of the manufacturing methods of the present invention is to dissolve a water-soluble Ni compound in an aqueous solution of 39 to 17 g/'II as metal Ni and a water-soluble Zn compound in an amount of 6 to 68 g/4 as metal Zn,
Furthermore, 5 to 120 g/A' of Na25O,+, Aff
2 (SO4) q・14. -18H20 from 5 to 60
g/, n, H31303 at 5-40 g/(1,
3-15g/jl of sodium naphthalene disulfonate
' , N') (, p I in which one or more types of CI are added and dissolved within the range of 90 to 250 g/II
(It is characterized by plating a Zn-Ni alloy on the surface of a Cu or Cu alloy strip by electrolyzing using an electrolyte of 0.9 to 5.8 and using the Cu or CU alloy strip as a cathode. .

Another method of the present invention is to use a water-soluble Ni compound containing 39 to 77 g/A of metal Ni! In addition, 5 to 120 g/l of Na2SO4 was added to an aqueous solution containing 6 to [i8 g/l2 of a water-soluble Zn compound as metal Zn, A1
2 (SO4)* ・I4- +8H20 from 5 to 60
g/l, H3BO, 5-4Qg/l, sodium naphthalene disulfonate 3-I 5g/II, N
By electrolyzing H4C7+ using a Cu or Cu alloy strip as a cathode using an electrolytic solution with a pH of 0.9 to 5.8 in which one or more of H4C7+ is added and dissolved in the range of 90 to 25 [1g/7I]. The method is characterized in that after the surface of Cu or Cu alloy strip is plated with Zn-Ni alloy, it is subjected to heating diffusion treatment or heating diffusion treatment and rolling processing.

[Effect]

That is, in the manufacturing method of the present invention, Zn-Ni alloy with excellent corrosion resistance is plated on the surface of Cu or Cu alloy strip.
Z
As the water-soluble Zn compound and Ni compound used as the plating solution for the n-Ni alloy, sulfates or chlorides can be used.

However, the composition of the plating solution was limited as described above, and the metal Ni concentration in the plating solution was made into a high-concentration bath of 39 to 11 g/Il. By using Zn-Ni alloy plating, single Zn plating This is because the cathode current efficiency is lower than in the case of , and it is necessary to compensate for this to some extent.

In order to obtain a plating film with uniform appearance and good gloss, it is necessary to change the bath composition depending on the current density range.
Preferably 5 to +5 A/d%.

Good plating can be obtained at a metal Zn concentration of 42 to 68 g/l of 20 A/dd or more, preferably 30 A/dd or more. However, if the metal Zn concentration is less than the lower limit, the Ni content in the plating film will increase, but the corrosion resistance improvement effect will be diminished and it will be economically disadvantageous.
The concentration becomes too high and no improvement in corrosion resistance can be expected.

The cathode current efficiency varies depending on conditions such as bath composition and current density, but for example, ZnSO47H2080g/A
! (18 g/l as metal Zn).

N15Oa 6H20300g/n (67g/l as metal Ni), Na25Oa 100g/l.

Al2 (S O4) 3・1418H2030g/
In a plating bath containing V and pH 1.3 to 1.7, the cathode current efficiency is about 80 to 85% at current density + OA/d%, but when N]SO4.6H20 is added at 150 g/n
(37 g/j+ as metallic Ni), the cathode current efficiency decreases to about 60%. Also ZnSO4/7
H20100g/I (34.2g/l as metal Zn
), N i S 04 ・6H20300g/A'
(66g/Il as metal Ni), Na2so
, l Io(Ig/l, AA' 2 (S O
4) In a plating bath with a pH of 2.0 to 2.5 containing 3 ・14-18H2030 g/l, a plating film with uniform glossiness can be obtained at a current density of about 25 A/dd or less at a plating thickness of 5 μ. However, if it exceeds 30^/dn-r, the glossiness deteriorates and becomes matte. ZnSO4
・7H20 at 250 g/A' (57 as metal Zn
g/7), the plated film becomes matte at 2OA/drd or less, but a plated film with uniform glossiness is obtained at 30A/dd or more.

In terms of corrosion resistance, the Ni content of Zn-Ni alloy plating is preferably about 8 to 15 wt%, and for this purpose, the metal Nj concentration during plating should be 53 to 73 g/n, and 5 to +5 Aldi. In order to obtain a plating film with a uniform appearance and good gloss at a current density, the Zn/Ni weight ratio in the bath should be 175 to 415, and a plating film with a uniform appearance and good gloss at a current density of 30 A/dd or higher. For this reason, it is desirable that the Zn/N1 weight ratio in the bath is 415 to 1/l.

The addition of Na2SO4 improves the conductivity of the plating solution and improves the conductivity of the Al
The addition of 2 (SO4)3.14-+8H20 and sodium naphthalene disulfonate improves the gloss of the plating, and the addition of H3BO1 and NH4Cl adjusts the pH of the plating solution, both of which were controlled within the above range. This is because there is no effect when the lower limit is less than the lower limit, and there is no improvement effect when the upper limit is exceeded, which is economically disadvantageous. In addition, the pH of the plating solution was specified as 0.9 to 5.8 because good Zn-Ni alloy plating can be obtained within this range, and good Zn-Ni alloy plating cannot be obtained outside this range. It's for a reason.

The heat diffusion treatment after Zn-Ni alloy plating strengthens the adhesion between the plating layer and the core material through mutual diffusion, and
This is to improve the sacrificial anode effect, and the rolling process, together with heating and diffusion, improves adhesion, improves dimensional accuracy, and improves the strength of the fin hole by making the plating layer a processed structure. It's for a reason. Although the uninvented effect can be obtained by performing either the heat diffusion treatment or the rolling process first, it is desirable to perform the rolling process in the final step.

〔Example〕

Using a heat-resistant copper strip (conductivity 95% 1^C8) containing 0.038 mm thick MgO, 02 wt%, Zn-Ni alloy plating with a thickness of 1.2 μm was applied to both sides using the plating bath below. Corrosion tests were conducted on the applied specimens, and the rate of deterioration of tensile strength was measured. The result was a pure Zn film with a thickness of 1.2μ.
Table 1 shows a comparison with the conventional method of plating.

Table 1 also shows the appearance when plated to a thickness of 5μ.

The corrosion test consisted of spraying salt water based on Its Z237+ for 1 hour and then holding the sample in a constant temperature and humidity layer at 70° C. and 95% humidity for 23 hours, which was repeated 30 times.

Plating bath (1) NiS()+ ・6 H20300g# (67g/l as metal Ni) n504 ・7H2080g# (18g/l as metal Zn) aSO4 A42 (SO4)3 ・14H Temperature current density plating bath (2) N i C12 ・6 H20180g# (44g/V as metal Ni) 100g/il! 18H2030g/l 1.5 50℃ 5^/drrf nCn 2 80g, # (38g/l as metal Zn) H4CI 3 BO3 H Temperature current density 230g#+ 20g/l! 30℃ 5A/drrr Plating bath (3) NiSO4・6H20300g#! (66g/l as metal Ni) Zn SO4' 7H2080g/l (57g/l as metal Zn) Na SO4 An 2 (SO4) 3 ・14H Temperature current density plating bath (4) 1Cn2 ・6H202g3g/jl! (70g/A' as metal Ni) 100g/A'18H2030g# 1.5 50℃ 35^/dffl nC12 135g#! (51 g/l as metal Zn) H4CI H'+ B O'+ H Temperature current density 230 g/I! 20g#5.0 30℃ 35^/dnf Plating bath (5) NiSO.

nSO4 ・6H2080g#! (18g/A' as metal Ni) ・7H20240g/A' (55g/42 as metal Zn) aSO4 A(12(SO4) s ・14 H Temperature current density plating bath (6) 1SO4 ・6H20150g# (As metal Ni 33g/l) 100g#' 18H, 030g/l 50℃ 5 A/d-Zn5Oa' 7H20250g/l (57g/A' as metal Zn) N a S Oa AA' 2 (SOa ) q ・14H Temperature current density 100g /A'18H2030g#2.5 50℃ 35^/drrr Plating bath (7) Zn So4-7H20240g#! (55g/j+ as metal Zn) Na, So.

A12 (S04 H Temperature current density 100g#) 3 ・14 18H2030g#2 1.5 20°C 35^/d As is clear from Table 1, the conventional method No. 7, which plated pure Zn, It can be seen that while the strength deterioration due to corrosion is significant, the strength deterioration is small in the specimens according to the present invention methods No. 1 to 4, and the corrosion resistance is improved.

On the other hand, comparative method No. 1 has a lower metallic Ni content in the plating bath.
, 3 to 4, it can be seen that the strength deterioration is significant.

. Next, a heat-resistant copper strip (conductivity 95.5% lAC3) containing MgO102W (95.5% AC3) with a thickness of 0.065 mm was used, and using the plating baths (1) to (7) described above, a Z layer with a thickness of 2.4 μ was applied to both sides.
After applying n-Ni alloy plating, heat diffusion treatment was performed at 500℃ for 1 minute, and this was rolled to a thickness of 0.035+ nm.
It was used as a fin material.

A test similar to the corrosion test described above was conducted on this to measure the deterioration rate of tensile strength. After plating pure Zn with a thickness of 24μ, the result was heated and diffused at 450°C for 1 minute, and then rolled to a thickness of 0.036m.
Table 2 shows a comparison with the conventional method where m is used.

As is clear from Table 2, conventional methods No. and I4, in which pure Zn was plated and then heat-diffused and rolled, were dezinced and the strength deteriorated significantly, whereas inventive method No. Those according to 8 to 11 have less dezincing,
It can be seen that the strength deterioration is small.

On the other hand, comparative method No. 1 has a lower metallic Ni content in the plating bath.
, Nos. 12 and 13 show significant dezincing and significant strength deterioration.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to effectively improve the corrosion resistance of the copper heat exchanger fin material and to suppress a decrease in thermal conductivity, thereby improving the service life of the heat dissipation fin. This has significant industrial effects, such as making it possible to achieve thinner walls and lighter weight.

Claims (2)

[Claims] (1) 39 to 77 g of water-soluble Ni compound as metal Ni
In addition, Na_2
5 to 120 g/l of SO_4, Al_2(SO_4)_
3.14-18H_2O 5-60g/l, H_3BO
5 to 40 g/l of _3, 3 to 15 g/l of sodium naphthalene disulfonate, 90 to 250 g of NH_4Cl
By electrolyzing the Cu or Cu alloy strip as a cathode using an electrolytic solution with a pH of 0.9 to 5.8 in which one or more of them are added and dissolved within the range of A method for producing a fin material for a copper heat exchanger, the method comprising plating the surface with a Zn-Ni alloy. (2) 39 to 77 g of water-soluble Ni compound as metal Ni
/l and water-soluble Zn compound as metal Zn 6 to 42g/l
In addition, 5 to 50% of Na_2SO_4 is added to the aqueous solution in which
120g/l, Al_2(SO_4)_3・14-18
H_2O 5-60g/l, H_3BO_3 5-40
g/l, sodium naphthalene disulfonate from 3 to 15
g/l, NH_4Cl in the range of 90 to 250 g/l, pH 0.9 to 5, with one or more types added and dissolved.
．． By electrolyzing the Cu or Cu alloy strip using the electrolytic solution No. 8 as a cathode, Zn is deposited on the surface of the Cu or Cu alloy strip.
- A method for producing a fin material for a copper heat exchanger, which comprises plating with a Ni alloy and then subjecting it to a heating diffusion treatment, or subjecting it to a heating diffusion treatment and a rolling process.