GB2046302A

GB2046302A - Zinc alloy powder

Info

Publication number: GB2046302A
Application number: GB8006543A
Authority: GB
Original assignee: Mitsui Mining and Smelting Co Ltd
Current assignee: Mitsui Mining and Smelting Co Ltd
Priority date: 1979-03-02
Filing date: 1980-02-27
Publication date: 1980-11-12
Also published as: DE3007850A1; CA1158461A; FR2450281A1; FR2450281B1; DE3007850C2

Abstract

Zinc-based alloy powders for use in mechanical plating of a substrate include Zn-Al, Zn-Al-Cu, An-Al- Mg, An-Al-Cu-Mg and other zinc alloys containing at least one of the metals selected from Ni, Si, Ti, Sb, Ag, Cr, Be, Ca, Co, Na, K, In, Li and Sr. Powders of these zinc alloys give tight adhesion of film coated onto a substrate, and excellent corrosion resistance when they are used in mechanical plating as compared with conventional mechanical plating using zinc powder. The alloys disclosed contain one or more of 0 &cirf& 1=60%Al, up to 5% Ni, up to 3% each Mg and Cu, up to 2% Si, up to 1 &cirf& 5% Ti, up to 1% each of Sb and Ag, up to 0.5% each of Cr and Be, up to 0 &cirf& 1% each of Ca, Co, Na, K and In and up to 0 &cirf& 05% each of Li and Sr.

Description

SPECIFICATION Zinc alloy powder for use in mechanical plating This invention relates to a zinc alloy powder for use in mechanical plating.

In general, as metallic coating processes of various iron products, copper products and the like for improving the appearance and corrosion resistance of those products, there are known the processes in which said products are coated with a molten metal by means of metal spraying, vaporization or direct dipping into the molten metal, as well as the so-called electroplating by which a metal to be coated is deposited electrically and the process in which the products are coated mechanically.Among these processes, the mechanical coating process, i.e. the mechanical plating process, is advantageous in that a coating of given thickness can be produced easily with a relatively simple apparatus so that the cost is low, and that faults observable in the other coating processes such as hydrogen embrittlement, blister, etc. do not appear at all, and this process is extensively employed currently. As plating materials for this process, powders of Zn, Cd, Sn, Pb, Sn-Zn alloy, Sn-Cd alloy and the like are used, among which Zn powder occupies the major part of the use.

Mechanical plating with such conventional compositions results in insufficient corrosion resistant properties at circa 10 jum film thickness to withstand the 120-150 hour Neutral-Salt Spraying test, so that rust on the bare metal substrate can be seen. Thus, stronger corrosion resistance has been desired. Even where corrosion resistance is satisfactory, the thickness of the film would be unnecessarily thick, which is clearly uneconomical; there were some cases where adhesion was lowered thereby.

With the aim of improving the corrosion resistance of mechanical plating, the present inventors paid attention to the powder itself as a mechanical plating material and conducted extensive studies thereon. As the result, it was found that the corrosion resistance can be improved drastically and, at the same time, a good adhesion of coating film can be obtained by using, as a mechanical plating material, Zn-Al alloy powder, of which utilization in the powdery form has by no means been conceived hitherto though it has been used hitherto in zinc die casting, hot dip galvanizing, electroplating, etc. Furthermore, it was also confirmed that even some zinc alloy powders other than Zn-Al alloy powder can also improve the corrosion resistance, and in addition, that further improvement of the corrosion resistance can be achieved by incorporating a certain kind of additive elements to Zn-Al.

Thus, according to this invention, there is provided a zinc alloy for use in mechanical plating which contains in Zn ingot at least one of metals with their contents selected from the group consisting of Al = 0.1-60, 5.0, Mg 5 Mg3.0, Cu Cu3.0, Sii 2.0, Ti 1.5, Sb 4 1.0, Ag ~ 1.0, Cr ~ 0.5, Be ~ 0.5, Ca ~ 0.1, Co c 0.1, Na ~ 0.1, K < 0.1, In ~ 0.1, Li ~ 0.05, and Sr ~ 0.05 (each percent by weight).

Thus, actual examples of the materials from which the zinc alloy powder of the present invention for use in mechanical plating is to be produced include Zn-Al, Zn-Al-Cu, Zn-AI-Mg, Zn Al-Cu-Mg and other zinc alloys obtainable by incorporating at least one of the other metals mentioned above into zinc or said alloys.

If the content of individual additive element exceeds its own upper limit as above, it may lead to various harmful effects such as formation of intermetallic compound exercising an adverse influence upon adhesion, impossibility in alloying with zinc and formation of needless oxides. If the content of individual additive element is less than 0.01% by weight, no improvement of corrosion resistance may be observed sometimes with one additive element alone but even in such a case the effect can be exhibited by adding two or more of additive elements or owing to the coexistence with Al. Regarding the content of Al, no improvement in corrosion resistance is observable when Al content is less than 0.1% by weight, while the coating cannot be practised sufficiently when Al content exceeds 60% by weight.When Al content is 55% by weight or more, the adhesion becomes somewhat poor. Accordingly, the content of Al should be in the range of 0. 1-60% by weight and preferably in the range of 2-55% by weight. Thus, Al is preferred as an alloying metal but not a prerequisite to obtaining an alloy which can function in accordance with the objectives of the invention. In addition to or in place of Al, at least one of the above alloying elements with their percentages may be incorporated.

Such alloy powders can be produced by adding a given amount of the respective additive elements to Zn ingot to adjust the composition of alloy to be produced, and followed by any processes other than the distillation process, for example, by means of mechanical processes such as dropping, graining, atomizing, grinding or the like, or dry or wet reduction process, electrolytic process, substitution process or the like, among which atomizing process is most preferable. Thus, fine Zn alloy powders having a diameter of 1-20 ym and preferably 5-10 ym can be obtained.

In this invention, there is no substantial inconvenience even if one or more of Pb < 1.30% by weight, Fe < 0.025% by weight, Cd < 0.40% by weight or Sn < 0.10% by weight are present in the zinc ingot as possible impurities. Accordingly, any of the distilled zinc ingots having a purity of grade 1 or higher, according to JIS H 2107, may be used in the present invention.

The substrate to be coated with the zinc alloy powder is not limited to metallic substrates such as iron, copper, brass and the like but it may also be nonmetallic ones. Further, the corrosion resistance can be much more improved if a conventional mechanical plating procedure is applied onto such a substrate with the zinc alloy powders of the present invention and then, for example, a chromate treatment is carried out thereon.

The zinc alloy powders of this invention mentioned above satisfy the requirements regarding the characteristic properties necessary to the use in mechanical plating, such as activity to chemicals, particle size, shape and the like. Accordingly, when they are used for mechanical plating, the adhesion between metallic substrate and coating film is improved and that, the corrosion resistance of coating film increases about 2 to 10 times the conventional cases.

Consequently a very desirable coating film can be formed, in addition to the advantages hitherto known in the mechanical plating.

Embodiments of this invention will be illustrated below as Examples.

Examples After having formulated the components so as to give the composition as shown in the following table, according to the atomizing process the mixture was molten at 450-800'C, the molten metal was rapidly cooled by injecting it with gas from a nozzle, and the powders thus obtained were subjected to surface cleaning and conditioning, drying and classification to give fine powders having a mean particle diameter of 6-8 ym.

By using these powders, mechanical platings were carried out according to the known method. Thus, after degreasing a substrate to be treated, it was subjected to surface cleaning and conditioning, and flash-coating to form plating while tumbling it with an impact media and chemical agents in a rotating barrel. Thereafter, it was water-flooded and polished, after-treated, again water-washed and dried to obtain a film having a thickness of about 10 ym.

The film thus obtained were examined for adhesion and for corrosion resistance after chromate treatment. The adhesion was evaluated by a method which comprises attaching the commecially available scotch tape No. 600 onto the surface of plating, peeling off the tape and then observing the coverage and adhesion of powder to the tape surface, and by a method which comprises microscopically observing the cross section of the plated body. The results of the tape peeling test were numerically expressed according to the five rank standard of evaluation as shown in Fig. 1. The corrosion resistance was evaluated according to the neutral salt spray test (JIS Z 2371) by measuring the time period required for forming red rust in term of hour. It is generally considered that a corrosion resistance of 240 hours or more is desirable.

Results of the examinations are summarized in Tables A and B. The states of the films which were evaluated as "very good" and as "bad" in the adhesion test are shown in Fig. 2 (sample No. A-18) and Fig. 3 (sample No. A-16), respectively.

Samples No. A-1 to A-3 are control examples by the use of zinc powder.Samples No. A-4, A-16, A-20 and A-22 are out of the scope of this invention, and Samples No. B-1-2 are control examples by the use of Zn powder alone. Samples No. B-12, B-16, B-20, B-27, B-30, B-39 and B-1 11 to B-113 are out of the scope of this invention.

Table A Composition of powder (% by wt.) Sample No.

A- Al Cu Mg Pb Fe Cd Sn Sb Zn 1 - - - < 0.003 < 0.002 < 0.001 - - Remainder 2 - - - < 0.003 < 0.002 < 0.001 - - Remainder 3 - - - 1.29 0.024 0.38 0.09 0.09 Remainder 4 0.05 - - < 0.003 < 0.002 < 0.001 - - Remainder 5 0.10 - - < 0.003 < 0.002 < 0.001 - - Remainder 6 0.10 2.0 2.0 < 0.003 < 0.002 < 0.001 - - Remainder 7 1.0 - - < 0.003 < 0.002 < 0.001 - - Remainder 8 1.0. 1.0 - < 0.003 < 0.002 < 0.001 - - Remainder 9 1.0 2.0 - < 0.003 < 0.002 < 0.001 - - Remainder 10 1.0 - 1.0 < 0.003 < 0.002 < 0.001 - - Remainder 11 1.0 - 2.0 < 0.003 < 0.002 < 0.001 - - Remainder 12 1.0 1.0 1.0 < 0.003 < 0.002 < 0.001 - - .Remainder 13 5.0 - - < 0.003 < 0.002 < 0.001 - - Remainder 14 5.0 - - 1.29 0.024 0.38 0.09 0.09 Remainder 15 10.0 - - < 0.003 < 0.002 < 0.001 - - Remainder 16 10.0 4.0 4.0 < 0.003 < 0.002 < 0.001 - - Remainder 17 15.0 - - < 0.003 < 0.002 < 0.001 - - Remainder 18 22.0 - - < 0.003 < 0.002 < 0.001 - - Remainder 19 22.0 2.0 - < 0.003 < 0.002 < 0.001 - - Remainder 20 22.0 4.0 - < 0.003 < 0.002 < 0.001 - - Remainder 21 22.0 - 2.0 < 0.003 < 0.002 < 0.001 - - Remainder 22 22.0 - 4.0 < 0.003 < 0.002 < 0.001 - - Remainder 23 22.0 2.0 2.0 < 0.003 < 0.002 < 0.001 - - Remainder 24 55.0 - - < 0.003 < 0.002 < 0.001 - - Remainder 25 65.0 - - < 0.003 < 0.002 < 0.001 - - Remainder Table A (Cont'd) Mean Adhesion par- Corrosion ticle Evaluation Evaluation by resistance Zinc ingot size tape peeling observation of (hr) ( m) test cross section 6 4 Very good 150 Purest zinc ingot 8 4 ii T50 Purest Zinc ingot 6 4 11 120 Distilled zinc ingot grade 1 6 4 1 50 Purest zinc ingot 8 4 II 290 Purest zinc ingot 8 4 " 360 Purest zinc ingot 8 4 " 400 Purest zinc ingot 8 4 " 450 Purest zinc ingot 8 4 " 500 Purest zinc ingot 8 4 " 480 Purest zinc ingot 8 4 Ii 600 Purest zinc ingot 8 4 ii 500 Purest zinc ingot 8 4 Very good 600 Purest zinc ingot 6 4 " 600 Distilled zinc ingot grade 1 8 4 1I 600 Purest zinc ingot 8 2 Poor 600 Purest zinc ingot 8 4 Very good 530 Purest zinc ingot 8 4 I1 530 Purest zinc ingot 8 4 " 580 Purest zinc ingot 8 1 Bad 580 Purest zinc ingot 8 4 Very good 600 Purest zinc ingot 8 1 Bad 600 Purest zinc ingot 8 4 Very good 700 Purest zinc ingot 8 3 Very good 600 Purest zinc ingot 8 2 Poor 600 Purest zinc ingot Table B Composition of powder (% by wt.) Adhesion Corro sion Sample Evalua- Evaluation resist- Zinc ingot No. Others Others tion by by observa- ance B- Al Cu Mg 1 2 tape tion of (hr) peeling cross test section 1-2 - - - - - 4 Very good 120-150 Purest, distilled 3 0.1 - - - - 4 " 290 Purest 4 1.0 - - - - 4 " 400 5 5.0 - - - - 4 " 600 6 10 - - - - 4 " 600 7 15 - - - - 4 " 530 8 22 - - - - 4 " 530 9 55 - - - - 3 Good 600 10 - - - Ni 1.0 - 4 Very good 300 11 - - - Ni 5.0 - 3 Good 350 12 - - - Ni 6.0 - 2 Poor 350 13 - - 0.1 - - 4 Very good 300 14 - - 1.0 - - 4 Very good 400 15 - - 3.0 - - 4 " 400 16 - - 4.0 - - 2 Poor 500 17 - 0.1 - - - 4 Very good 300 18 - 1.0 - - - 4 ii 400 Purest 19 - 3.0 - - - 4 " 400 20 - 4.0 - - - 2 Poor 400 21 - - - Si 1.0 - 4 Very good 300 22 - - - Si 2.0 - 4 " 300 23 - - - Si 3.0 - 2 Poor 300 24 - - - Ti 0.1 - 4 Very good 300 25 - - - Ti 0.3 Cr 0.1 4 " 350 26 - - - Ti 1.5 - 4 " 300 27 - - - Ti 2.0 - 2 Poor 300 28 - - - Sb 0.1 - 4 Very good 300 29 - - - Sb 1.0 - 4 " 300 30 - - - Sb 1.5 - 2 Poor 300 31 - - - Ag - 4 Very good 350 32 - - - Cr 0.5 - 4 " 400 33 - - - Be 0.1 - 4 " 300 34 - - - Be 0.5 - 4 " 350 35 - - - Ca 0.1 - 4 " 300 36 - - - Co 0.1 - 4 " 350 37 - - - Na 0.05- 4 Very good 400 38 - - - Na 0.1 - 4 " 450 39 - - - Na 0.2 - 2 Poor 450 40 - - - K 0.1 - 4 Very good 400 41 - - - In 0.1 - 4 " 300 42 - - - Li 0.05 - 4 " 350 43 - - - Sr 0.05 - 4 " 350 44 - - - Ni 1.0 Cr0.5 4 " 400 45 - - - Ni 1.0 Co 0.1 4 " 400 46 - - - Ni 1.0 Sb 1.0 4 " 400 47 - - - Ni 1.0 Ti0.5 4 " 400 48 - - - Ni 1.0 Na 0.05 4 " 400 49 - - - Ni 1.0 Li 0.05 4 " 450 50 5.0 - - Ni 1.0 - 4 " 700 51 5.0 - - Ni 5.0 - 4 " 800 52 5.0 - - Si 1.5 - 4 " 650 53 5.0 - - Ti 1.0 - 4 " 700 Table B (Cont'd) Composition of powder (% by wt.) Adhesion Corro sion Sample Evalua- Evaluation resist- Zinc ingot No.Others Others tion by by observa- ance B- Al Cu Mg 1 2 tape tion of (hr) peeling cross test section 54 5.0 - - Sb 1.0 - 4 ii 700 55 5.0 - - Ag 1.0 - 4 " 700 56 5.0 - - Cr 0.5 - 4 " 700 57 5.0 - - Be 0.5 - 4 " 750 58 5.0 - - Ca 0.1 - 4 Very good 700 59 5.0 - - Co 0.1 - 4 " 750 60 5.0 - - Na 0.1 - 4 " 1500 61 5.0 - - K 0.1 - 4 " 750 62 5.0 - - In 0.1 - 4 " 700 63 5.0 - - Li 0.05 - 4 " 750 64 5.0 - - Sr 0.05 - 4 " 750 65 5.0 - - Ti 1.0 Cr 0.5 4 " 750 66 5.0 - - Ni 1.0 Ti 1.0 4 " 800 67 10 - - Si 1.5 - 4 " 750 68 10 - - Na 0.1 Ni 1.0 4 " 800 69 22 - - Si 1.5 Ti 1.0 4 " 800 70 22 - - Cr 0.5 Be 0.5 4 " 800 71 55 - - Ni 0.1 Be 0.1 4 " 800 72 55 - - Na 0.1 Be 0.1 4 " 800 73 0.1 0.05 - Ni 0.1 Ti 0.1 4 " 350 74 0.1 0.05 0.05 In 0.1 Na 0.1 4 " 550 75 0.1 - 0.05 Ni 0.1 Ti 0.1 4 " 500 76 0.5 - 0.05 Ni 0.1 Co 0.1 4 " 500 77 1.0 0.5 0.1 Na 0.05K 0.05 4 " 500 78 1.0 - 0.05 Be 0.1 - 4 " 500 79 4.0 - 0.05 Ni 0.01 - 4 Very good 800 80 4.0 3.0 - Be 0.05 - 4 " 800 81 4.0 - 1.0 Be 0.05 Ni 0.1 4 " 850 82 4.0 1.0 1.0 Be 0.05 - 4 " 1000 83 4.0 3.0 1.0 Be 0.05 Ti 0.1 4 " 1500 84 4.0 3.0 0.05 Si 0.1 Be 0.1 4 " 1500 85 4.0 3.0 0.1 Ti 0.1 Ag 0.1 4 " 1000 86 4.0 3.0 0.05 Be 0.1 Ag 0.1 4 " 1000 87 5.0 1.0 0.1 Be 0.1 Ti 0.1 4 " 900 88 5.0 - 0.1 Sb 0.1 Be 0.1 4 " 900 89 5.0 - 0.1 Sb 0.1 Ti 0.1 4 " 900 90 5.0 - 0.1 Si 1.0 - 4 " 900 91 5.0 1.0 1.0 Sb 1.0 - 4 " 1000 92 10 1.0 - Na 0.1 - 4 " 900 93 10 1.0 - Co 0.1 - 4 " 900 94 10 1.0 0.1 Na 0.1 - 4 " 900 95 12 1.0 0.05 Be 0.1 Ti 0.1 4 " 1000 96 12 1.0 0.05 Ti 0.1 Cr 0.1 4 " 900 97 22 0.1 - Si 1.0 - 4 " 800 98 22 0.1 0.1 Ti 0.1 - 4 " 800 99 22 0.5 - Ni 0.1 - 4 " 900 100 22 0.5 0.1 Ni 0.1 Ti 0.1 4 101 22 0.5 0.1 Si 1.5 - 4 Ve,y,900d or 900 900 102 55 3.0 - Si 1.5 - 4 " 1000 103 55 - 3.0 Si 1.5 - 4 " 1000 104 55 3.0 3.0 Si 1.5 - 4 " 1000 105 55 2.0 - Ti 0.1 Co 0.1 3 Good 900 106 55 2.0 - Si 1.5 Be 0.1 3 " 900 Table B (Cont'd) Composition of powder (% by wt.) Adhesion Corro sion Sample Evalua- Evaluation resist- Zinc ingot No. Others Others tion by by observa- ance B- Al Cu Mg 1 2 tape tion of (hr) peeling cross test section 107 55 - 2.0 Ca 0.1 Cr 0.5 3 " 1000 108 55 - 2.0 Sb 1.0 Sr 0.05 3 " 1000 109 55 2.0 2.0 Ag 0.5 Li 0.05 3 " 1200 110 55 2.0 2.0 Si 1.5 Ti 1.0 3 1200 111 65 1.0 - Ni 1.0 - 2 Poor 1200 112 65 - 1.0 Ti 1.0 - 2 " 1200 113 65 1.0 1.0 Si 1.5 - 2 " 1000

Claims

1. A zinc alloy powder for use in mechanical plating comprising zinc ingot as base metal and one or more members selected from the group consisting of Al 0.1-60, Ni 5 5.0, Mg ' 3.0, Cu # 3.0, Si # 2.0, Ti # 1.5,Sb # 1.0, Ag # 1.0, Cr # 0.5, Be # 0.5, Ca # 0.1, Co # 0.1, Na # 0.1, K # 0.1, In # 0.1, Li # 0.05 and Sr # 0.05, each being in percent by weight of the total alloy except the weight of impurities.

2. A zinc alloy powder for use in mechanical plating according to Claim 1 which contains 0.1-60% by weight of Al.

3. A zinc alloy powder for use in mechanical plating according to Claim 2 which contains one or two member(s) selected from Cu # 3.0% by weight and Mg # 3.0% by weight, in addition to said 0.1-60% by weight of Al.

4. A zinc alloy powder for use in mechanical plating according to Claim 2 or 3 which additionally contains one or more members selected from the group consisting of Ni # 5.0, Si # 2.0, Ti 1.5, Sb ' 1.0, Ag ' 1.0, Cr Cr # 0.5, Be # 0.5, Ca # 0.1, Co # Na # 0.1, K # 0.1, In = 0. 1 Li ~ 0.05 and Sr 5 0.05 each being percent by weight of the total alloy except the weight of impurities.

5. A zinc alloy powder for use in mechanical plating substantially as hereinbefore described in the non-comparative examples.