METHOD OF MEASURING THE CONTENT OF A CHEMICAL ELEMENT IN A COATING

Abstract

A method of measuring content of a first chemical element in a coating comprising the first element applied on a substrate also comprising the first element, the content of said the element being determined by measuring the ratio of the content of a second chemical element over the content of the first element in the coating and the ratio of the content of the second element over the content of the first element in the substrate, whereby the content of the first element both in the coating and in the substrate is different than the content of the second element both in the coating and in the substrate and the ratio of the content of a second element over the content of the first element in the coating is different from the ratio of the content of the second element over the content of the first element in the substrate.

Claims

1-15. (canceled)

16. A method of measuring the content of a first chemical element in a coating comprising said first chemical element applied on a substrate also comprising said first chemical element, whereby the content of said first chemical element is determined by means of measuring the ratio of the content of a second chemical element over the content of said first chemical element in the coating as well as the ratio of the content of said second chemical element over the content of said first chemical element in the substrate, whereby further the content of the first chemical element both in the coating and in the substrate is different than the content of the second chemical element both in the coating and in the substrate and further the ratio of the content of a second chemical element over the content of said first chemical element in the coating is different from the ratio of the content of said second chemical element over the content of said first chemical element in the substrate.

17. The method according to claim 16, whereby the content of the first chemical element both in the coating and in the substrate is higher than the content of the second chemical element both in the coating and in the substrate and/or whereby the first chemical element is iron and/or whereby the second chemical element may be selected from: manganese, chromium, silicon, vanadium, tungsten, nickel, molybdenum, aluminum, phosphor, sulfur, nitrogen or copper, preferably the second chemical element is manganese or silicon and/or whereby the substrate is steel.

18. The method according to claim 16, whereby the content of the first chemical element in the coating is determined by using the measured content of the first chemical element in the coating, the measured content of the second chemical element, and one or both ratios of content of the second chemical element over the content of the first chemical element selected from: (E2/E1).sub.deposited: the ratio of content of second chemical element over the content of the first chemical element in the coating, (E2/E1).sub.substrate: the ratio of content of second chemical element over the content of the first chemical element in the substrate, and/or whereby the content of the first chemical element in the coating is determined by the following formula: $E{1}_{\mathrm{coating}}=\frac{\left[\left(E{1}_{\mathrm{tot}}{\left(\frac{E2}{E1}\right)}_{\mathrm{substrate}}\right)-E{2}_{\mathrm{tot}}\right]}{\left({\left(\frac{E2}{E1}\right)}_{\mathrm{substrate}}-{\left(\frac{E2}{E1}\right)}_{\mathrm{deposited}}\right)}$ whereby E1.sub.coating is the relevant content of the first chemical element of the coating, E1.sub.tot represents the total measured content of the first chemical element of the coating and the substrate after a sample preparation, (E2/E1).sub.substrate represents the ratio of content of second chemical element over the content of the first chemical element in the substrate, E2.sub.tot is the total measured content of the second chemical element of the coating and the substrate after a sample preparation and (E2/E1).sub.deposited represents the ratio of content of second chemical element over the content of the first chemical element in the coating.

19. The method according to claim 16, whereby the iron content is determined by performing at least one dissolution step and by using the equation: ${\mathrm{Fe}}_{\mathrm{coating}}=\frac{\left[\left({\mathrm{Fe}}_{\mathrm{tot}}{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{steel}}\right)-{\mathrm{Mn}}_{\mathrm{tot}}\right]}{\left({\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{steel}}-{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{deposited}}\right)}$ whereby further Fe.sub.coating represents the iron content of the coating, Fe.sub.tot represents the total measured iron content of the steel substrate and the coating after a sample preparation, (Mn/Fe).sub.steel represents the ratio of the manganese content over the iron content of the steel substrate and may correspond to the following: (Mn/Fe).sub.steel+brass dissolution: the ratio of content of Mn over the content of the Fe measured in a first dissolution step, preferably a first passivation step, on a coating containing the same elements in same quantities but without first chemical element applied on the same substrate, (Mn/Fe).sub.dissolution: the ratio of Mn content over the content of Fe measured in a passivated or non-passivated environment (i.e. determined in a dissolution step carried out) on the bare substrate without coating, whereby further Mn.sub.tot represents the total measured manganese content of the steel substrate and the coating after a sample preparation, (Mn/Fe).sub.deposited represents the ratio of the manganese content of the coating over the iron content of the coating.

20. The method according to claim 16, whereby the iron content is determined by subjecting the coated steel to one or preferably more than one, further preferred 1 to 10, even further preferred 1 to 6 dissolution steps, even further preferred 1 dissolution step.

21. The method according to claim 16, whereby the iron content is determined performing n dissolution steps with n>1 and by using the equation: ${\mathrm{Fe}}_{\mathrm{coating}}=\frac{\left[\left({\mathrm{Fe}}_1.Math.{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{steel}+\mathrm{brass}\mathrm{dissolution}}\right)-{\mathrm{Mn}}_1\right]}{\left({\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{steel}+\mathrm{brass}\mathrm{dissolution}}-{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{deposited}}\right)}+\underset{i=2}{\overset{n}{.Math.}}\frac{\left[\left({\mathrm{Fe}}_{\left(i\right)}.Math.{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{dissolution}}\right)-{\mathrm{Mn}}_{\left(i\right)}\right]}{\left({\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{dissolution}}-{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{deposited}}\right)}$ whereby further Fe.sub.coating represents the iron content of the plated coating, Fe.sub.1 represents the iron amount determined in the first passivation step, (Mn/Fe).sub.steel+brass dissolution represents the ratio of content of Mn over the content of the Fe measured in a first step, preferably a first passivation step, on a coating containing the same elements in same quantities but without first chemical element applied on the same substrate, Mn.sub.1 represents the manganese amount determined in the first passivation step, (Mn/Fe).sub.deposited represents the ratio of the manganese content of the coating over the iron content of the coating, Fe.sub.(i) represents the iron amount determined in dissolution step i, (Mn/Fe).sub.dissolution represents the ratio of Mn content over the content of Fe measured in a passivated or non-passivated environment (i.e. determined in a dissolution step carried out) on the bare substrate without coating, Mn.sub.(i) represents the manganese amount determined in passivation step i.

22. The method according to claim 16, where values for Mn/Fe.sub.deposited<0.1%, preferably <0.04%, preferably <0.02% or <0.01% can be replaced by 0 in the formula(s).

23. The method according to claim 16, whereby the iron content is determined performing n dissolution steps with n>1 and by using the equation: ${\mathrm{Fe}}_{\mathrm{coating}}=\mathrm{Fe}1+\underset{i=2}{\overset{n}{.Math.}}\frac{\left[\left({\mathrm{Fe}}_{\left(i\right)}.Math.{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{dissolution}}\right)-{\mathrm{Mn}}_{\left(i\right)}\right]}{\left({\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{dissolution}}-{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{deposited}}\right)}$ whereby further Fe.sub.coating represents the iron content of the coating, Fe.sub.1 represents the iron amount determined in a first passivation step, (Mn/Fe).sub.deposited represents the ratio of the manganese content of the coating over the iron content of the coating, Fe.sub.(i) represents the iron amount determined in dissolution step i, (Mn/Fe).sub.dissolution represents the ratio of Mn content over the content of Fe measured in a passivated or non-passivated environment (i.e. determined in a dissolution step carried out) on the bare substrate without coating, Mn.sub.(i) represents the manganese content determined in dissolution step i.

24. The method according to claim 16, whereby the steel is in the form of a steel cord, and/or the coating comprises brass, and/or the coating may be brass enriched with iron, preferably comprises copper, zinc and iron, further preferred the coating comprises on average >55 wt.-%, preferably >60 wt.-%, further preferred >62 wt.-%, even further preferred >63.0 wt.-% of copper, 1 to 10 wt.-% of iron, preferably 2 to 6 wt.-% of iron and the remainder of zinc.

25. The method according to claim 16, whereby each dissolution step may be a passivation step or a corrosion step, and/or whereby a passivation step may comprises using a stripping solution capable of stripping the coating and passivating the substrate, preferable using an ammonia/ammonium persulfate solution, further preferred a solution comprising 16 g of (NH.sub.4).sub.2S.sub.2O.sub.8 and 120 mL NH.sub.3 (25 wt.-%) brought to 1 liter by addition of water, and/or whereby a corrosion step may be using water and/or acidic solution.

26. The method according to claim 16, whereby the content of chemical elements, especially iron and manganese, is determined by inductive coupled plasma spectroscopy, preferably inductive coupled plasma optical emission spectroscopy or by inductive coupled plasma mass spectroscopy or by UV-visible spectroscopy or by a combination of liquid chromatography and mass spectroscopy or by X-ray fluorescence spectroscopy or by atomic absorption spectroscopy.

27. The method according to claim 16, whereby each dissolution step is carried out under ultrasounds, preferably in an ultrasonic bath, for a duration of 5 to 480 minutes, preferably 10 to 90 minutes, further preferred 10 to 70 minutes, even further preferred >10 to 40 minutes, and/or whereby each dissolution step is carried out at a temperature between 0 to 80 C., preferably 5 to 60 C., further preferred 10 to 40 C., and/or whereby each dissolution step is carried out under ultrasounds, preferably in a ultrasonic bath, at a frequency of 20 to 100 kHz, further preferred 25 to 80 kHz.

28. The method according to claim 16, whereby at least one passivation step is carried out before one or more controlled corrosion step.

29. The method according to claim 16, whereby the coating is non-homogeneous, preferably in that it allows access to the underlying steel and/comprises brass rich regions, preferably comprising >95 w.%, further preferred >97 w.% of brass, and/or comprises iron rich particles, preferably comprising >95 w.%, further preferred >97 w.% of iron.

30. The method according to claim 16, whereby no further dissolution step is carried out when the last measure ratio of the content of manganese over the content iron is within the range of 50%, preferably 40%, further preferred 30%, further preferred 20%, further preferred 15%, of the ratio of the content of manganese over the content of iron of the steel substrate, and/or whereby a further dissolution step is carried out when that is not the case.

Description

EXAMPLES

Example 1

[0071] Sample A of steel substrates with a brass coating with average composition being 63.5 wt.-% Cu and the remainder being Zn as well as sample B of a steel cord with a coating having an average composition of 64 wt.-% of Cu and 4 wt.-% of Fe and the remainder being Zn applied to the half product were prepared. Samples A and B have been obtained by using a wet wire drawing step.

[0072] Samples A and B be were cut into pieces and 1.0 g of each sample was weighed on an electronic balance. The weighed samples were put into a test tube and 20 ml stripping solution was added into the tube. It is thereby important that the whole sample is submerged. If required, this may be achieved by selecting a test tube with an appropriate diameter.

[0073] 1 L of stripping solution can thereby be prepared by adding 16 g ammonium persulfate into a beaker of 600 ml, and dissolve with 400 ml in ultrapure water. The 400 ml solution is then transferred quantitatively to a 1000 ml volume flask before 120 ml of an ammonia solution (25 wt.-%) are added to the flask. The flask is then further filled to the 1 L mark by ultrapure water to obtain the stripping solution.

[0074] The test tube is put in a stainless basket and then is subjected to a high performance lab ultrasonic cleaner bath (for example supplied by Fisherscientific part of Thermo Fisher Scientific under the designation Fisherbrand FB 11209) for 60 min. Parameters of ultrasonic cleaner include the following. [0075] Frequency: 37 kHz [0076] Power: 100% [0077] Mode: pulse [0078] The temperature may thereby be kept between 2 and 40 C.

[0079] After ultrasonic treatment, the resulting solution is transferred to a volume flask of 200 ml via a funnel. 5 ml 37 wt.-% HCl are then added into volume flask. Moreover, about 20 ml of ultrapure water is added into each test tube to rinse each sample. The rinsing water is also added into the volume flask. The rinsing process continues with further 20 ml portions until the rinsing water in the tube is visually clear (i.e. transparent). The sample is then taken out of test tube and 5 ml 37 wt.-% HCl is added into the test tube to rinse the wall of tube with acid. The resulting solution is also transferred into volume flask. Last, ultra pure water is added to reach the grade mark of 200 ml, if required.

[0080] The concentration of Fe (mg/l) and Mn (mg/l) in the solution within volume flask is then determined by ICP-OES (Inductive Coupled Plasma Optical Emission Spectroscopy).

[0081] Calculation of Fe (mg) in the coating per kg cord is carried out via equation 1, 2 and 3.

[00005]$\begin{array}{cc}{\mathrm{Fe}}_{\mathrm{tot}}=\frac{{\mathrm{Fe}}_{\mathrm{flask}}*\mathrm{Flask}\mathrm{volume}}{\mathrm{Sample}\mathrm{weight}}& \left(\mathrm{Equation}1\right)\end{array}$$\begin{array}{cc}{\mathrm{Mn}}_{\mathrm{tot}}=\frac{{\mathrm{Mn}}_{\mathrm{flask}}*\mathrm{Flask}\mathrm{volume}}{\mathrm{Sample}\mathrm{weight}}& \left(\mathrm{Equation}2\right)\end{array}$$\begin{array}{cc}{\mathrm{Fe}}_{\mathrm{coating}}=\frac{{\mathrm{Fe}}_{\mathrm{tot}}*{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{steel}}-{\mathrm{Mn}}_{\mathrm{tot}}}{{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{steel}}-{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{deposited}}}& \left(\mathrm{Equation}3\right)\end{array}$ [0082] Fe.sub.flask: the Fe concentration in the volume flask as determined by ICP-OES, mg/l; [0083] Mn.sub.flask: the Mn concentration in the volume flask as determined by ICP-OES, mg/l; [0084] Flask volume: volume of flask (200 ml), ml; [0085] Sample weight: weight of sample, g; [0086] Fe.sub.tot: the total measured Fe (mg) per kg cord calculated based on Equation 1, mg/kg; [0087] Mn.sub.tot: the total measured Mn (mg) per kg cord, mg/kg calculated based on Equation 2; [0088] (Mn/Fe).sub.steel: ratio of Mn to Fe in the steel substrate; in present case, namely 0.0052 for both samples A and B based on the known steel composition as provided by the supplier; (Mn/Fe).sub.deposited: ratio of Mn to Fe in the coating of the respective half products before a wet wire drawing step; namely respectively 0.0146 and 0.0006 for samples A and B; [0089] Fe.sub.coating: the weight (mg) of Fe in the coating per kg sample calculated based on Equation 3.

[0090] Table 1 shows the data the data of two samples A and B each measured 3 times. For sample A the theoretical Fe.sub.coating should be 0 mg/kg and determinations indeed lead to values close to 0, indicating the method of the invention successfully distinguished between Fe from steel substrate and Fe from coating. On sample B, the determined Fe.sub.coating of the three measurements shows very little variation and is significantly different from 0.

TABLE-US-00001 TABLE 1 result of ICP test and calculated Fe (mg/kg) Sample Weight Fe.sub.flask Mn.sub.flask Fe.sub.coating+steel Mn.sub.coating+steel Fe.sub.coating Sample Measurement (g) (mg/l) (mg/l) (mg/kg) (mg/kg) (mg/kg) A 1 1.0194 0.2059 0.0011 40.40 0.22 1.43 2 1.0285 0.1850 0.0010 35.97 0.20 1.29 3 1.0185 0.2485 0.0013 48.81 0.26 0.83 B 1 1.0221 0.9202 0.0015 180.06 0.29 140.91 2 1.0019 0.9617 0.0016 191.98 0.32 146.99 3 1.0719 1.0063 0.0017 187.76 0.31 143.44

Example 2

[0091] Two pieces of sample C and D corresponding to 1 g+/0.05 are cut and placed in test tubes. In parallel, multiple flasks (of 100 ml) are prepared for further use by adding 10 ml of HCl 37 wt.-% and 5 ml of internal standard solution, which may be for example a solution containing 50 ppm scandium in 3 v-% HNO.sub.3 that may help to identify any possible measurement drifts).

[0092] The same high performance lab ultrasonic cleaner bath (see example 1 above) with the same parameters is used, whereby the bath temperature should be controlled between 3 and 40 C.

[0093] 10 ml of the same stripping solution (see example 1 above) is added into the test tubes. The test tubes are treated in the ultrasonic bath for 20 minutes. Afterwards the solution is transferred quantitatively into a flask, the sample itself is thoroughly rinsed in the funnel with ultrapure water, whereby the rinsing water is also transferred to the flask. The samples C and D are then brought back into the test tube. The flask is left to thermostatize at room temperature and after enough time (about 30-40 minutes) has passed, filled up to the mark with ultrapure water (leading to solutions C and D in Table 2 below).

[0094] Immediately after transferring the previous sample solution into a flask, sample C is once again treated with 10 ml of stripping solution, ensuring no or minimal exposure to a corrosive environment, to carry out a dissolution step being a passivation step. The test tube is then again placed into the ultrasonic bath and subjected to an ultrasound treatment for 20 minutes. Afterwards the solution is transferred quantitatively into a new flask, the sample itself is thoroughly rinsed in the funnel with ultrapure water. The sample is then brought back into the sample container. The flask is left to thermostatize at room temperature and after enough time has passed, filled up to the mark with ultrapure water. This procedure is then repeated 2 more times on sample C to carry out a total of 3 dissolution steps being passivation steps (leading to solutions C1 to C3 in Table 2 below).

[0095] On the other hand for sample D, immediately after transferring the previous sample solution into a flask as per paragraph [0048], sample D is treated with 5 ml of ultrapure water. The sample is then allowed to rest for 1 hour. Afterwards 10 ml of stripping solution is added to carry out a dissolution step being a corrosion step. The test tube is then again placed into the ultrasonic bath and subjected to an ultrasound treatment for 20 minutes. Afterwards the solution is transferred quantitatively into a new flask, the sample itself is thoroughly rinsed in the funnel with ultrapure water, whereby the rinsing water is also transferred to the flask. The cord sample is then brought back into the sample test tube. The flask is left to thermostatize and after enough time has passed, filled up to the mark with ultrapure water. This procedure is then repeated 2 more times on sample D to carry out a total of 3 dissolution steps being corrosion steps (leading to solutions D1 to D3 below).

[0096] Results determined by ICP-OES on the solutions for sample C are show in Table 2 below.

TABLE-US-00002 TABLE 2 Fe Mn Solutions (ppm/g) (ppt/g) C 1.115128 2370.562 C1 0.239258 643.2477 C2 0.073293 209.7134 C3 0.059897 273.617

[0097] Fe.sub.coating can thereby be determined as follows:

[00006]${\mathrm{Fe}}_{\mathrm{coating}}=\frac{\left[\left({\mathrm{Fe}}_1.Math.{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{steel}+\mathrm{brass}\mathrm{dissolution}}\right)-{\mathrm{Mn}}_1\right]}{\left({\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{steel}+\mathrm{brass}\mathrm{dissolution}}-{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{deposited}}\right)}+\underset{i=2}{\overset{n}{.Math.}}\frac{\left[\left({\mathrm{Fe}}_{\left(i\right)}.Math.{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{dissolution}}\right)-{\mathrm{Mn}}_{\left(i\right)}\right]}{\left({\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{dissolution}}-{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{deposited}}\right)}$${\mathrm{Fe}}_{\mathrm{coating}}=\frac{\left[\left(1,12.0,83\%\right)-0,0024\right]}{\left(0,83\%-0,07\%\right)}+\frac{\left[\left(0,37.1,13\%\right)-0,0011\right]}{\left(1,13\%-0,07\%\right)}$$\text{.1000}/10\mathrm{to}\mathrm{get}\mathrm{mg}/\mathrm{kg}\left(g\mathrm{to}\mathrm{kg}\mathrm{and}100\mathrm{mL}\mathrm{solution}\right)$${\mathrm{Fe}}_{\mathrm{coating}}=119,7\mathrm{mg}/\mathrm{kg}$

[0098] Fe.sub.coating thereby represents the iron content of the plated coating. Fe.sub.1 represents the iron amount determined by ICP-OES in the first passivation step and thus here on solution C.

[0099] (Mn/Fe).sub.steel+brass dissolution represents the ratio of content of Mn over the content of the Fe in a brass coating containing the same elements in same quantities but without Fe applied on the same substrate estimated based on Equation 4 below by ICP-OES on a solution obtained in a first passivation step as described in [0048],

[0100] Mn.sub.1 represents the manganese amount determined by ICP-OES in the first passivation step and thus here again on solution C.

[0101] (Mn/Fe).sub.deposited represents the ratio of the manganese content of the coating over the iron content of the coating determined by ICP-OES on the solution obtained by carrying out one passivation step as described above in [0048] on the corresponding half product before the wet wire drawing step.

[0102] Fe.sub.(i) represents the iron amount determined in dissolution step i and corresponds to the values determined by ICP-OES for the solutions C1 to C3, which may be added up in view of the formula above.

[0103] (Mn/Fe).sub.dissolution represents the ratio of Mn content over the content of Fe measured in a passivated or non-passivated environment (i.e. determined in a dissolution step carried out) on the bare substrate without coating and is determined for sample C as indicated in Table 4 below. Alternatively, (Mn/Fe).sub.dissolution can also be estimated based on steel composition of the steel substrate.

[0104] Mn.sub.(i) represents the manganese amount determined in passivation step i and again corresponds to the values determined by ICP-OES for the solutions C1 to C3, which may be added up in view of the formula above.

[0105] Alternatively, Fe.sub.coating can also be determined as follows:

[00007]${\mathrm{Fe}}_{\mathrm{coating}}=\mathrm{Fe}1+\underset{i=2}{\overset{n}{.Math.}}\frac{\left[\left({\mathrm{Fe}}_{\left(i\right)}.Math.{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{dissolution}}\right)-{\mathrm{Mn}}_{\left(i\right)}\right]}{\left({\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{dissolution}}-{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{deposited}}\right)}$${\mathrm{Fe}}_{\mathrm{coating}}=1,12+\frac{\left[\left(0,37.1,13\%\right)-0,0011\right]}{\left(1,13\%-0,07\%\right)}$$\text{.1000}/10\mathrm{to}\mathrm{get}\mathrm{mg}/\mathrm{kg}\left(g\mathrm{to}\mathrm{kg}\mathrm{and}100\mathrm{mL}\mathrm{solution}\right)$${\mathrm{Fe}}_{\mathrm{coating}}=140,6\mathrm{mg}/\mathrm{kg}$

[0106] Fe.sub.coating represents the iron content of the coating.

[0107] Fe.sub.1 represents the iron amount determined by ICP-OES in the first passivation step and thus here on solution C.

[0108] (Mn/Fe).sub.deposited represents the ratio of the manganese content of the coating over the iron content of the coating determined by ICP-OES on the solution obtained by carrying out one passivation step as described above in [0048] on the corresponding half product before the wet wire drawing step.

[0109] Fe.sub.(i) represents the iron amount determined in dissolution step i and corresponds to the values determined by ICP-OES for the solutions C1 to C3, which may be added up in view of the formula above.

[0110] (Mn/Fe).sub.dissolution represents the ratio of Mn content over the content of Fe measured in a passivated or non-passivated environment (i.e. determined in a dissolution step carried out) on the bare substrate without coating and is determined for sample C as indicated in Table 4 below. Alternatively, (Mn/Fe).sub.dissolution can also be estimated based on steel composition of the steel substrate.

[0111] Mn.sub.(i) represents the manganese amount determined in passivation step i and corresponds to the values determined by ICP-OES for the solutions C1 to C3, which may be added up in view of the formula above.

[0112] Results determined by ICP-OES on the solutions for sample D are show in Table 3 below.

TABLE-US-00003 TABLE 3 Fe Mn Solutions (ppm/g) (ppt/g) D 0.916177106 2185.813862 D1 1.183546044 5750.215983 D2 0.975597879 4801.20754 D3 0.452410171 2393.726684

[0113] Fe.sub.coating can thereby be determined as follows:

[00008]${\mathrm{Fe}}_{\mathrm{coating}}=\frac{\left[\left({\mathrm{Fe}}_1.Math.{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{steel}+\mathrm{brass}\mathrm{dissolution}}\right)-{\mathrm{Mn}}_1\right]}{\left({\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{steel}+\mathrm{brass}\mathrm{dissolution}}-{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{deposited}}\right)}+\underset{i=2}{\overset{n}{.Math.}}\frac{\left[\left({\mathrm{Fe}}_{\left(i\right)}.Math.{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{*\mathrm{dissolution}}\right)-{\mathrm{Mn}}_{\left(i\right)}\right]}{\left({\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{*\mathrm{dissolution}}-{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{deposited}}\right)}$${\mathrm{Fe}}_{\mathrm{coating}}=\frac{\left[\left(0,92.0,83\%\right)-0,0022\right]}{\left(0,83\%-0,07\%\right)}+\frac{\left[\left(2,61.1,13\%\right)-0,013\right]}{\left(0,60\%-0,07\%\right)}$$\text{.1000}/10\mathrm{to}\mathrm{get}\mathrm{mg}/\mathrm{kg}\left(g\mathrm{to}\mathrm{kg}\mathrm{and}100\mathrm{mL}\mathrm{solution}\right)$${\mathrm{Fe}}_{\mathrm{coating}}=122,7\mathrm{mg}/\mathrm{kg}$

[0114] Fe.sub.coating thereby represents the iron content of the plated coating.

[0115] Fe.sub.1 represents the iron amount determined by ICP-OES in the first passivation step and thus here on solution D.

[0116] (Mn/Fe).sub.steel+brass dissolution represents the ratio of content of Mn over the content of the Fe in a brass coating containing the same elements in same quantities but without Fe applied on the same substrate estimated based on Equation 4 below by ICP-OES on a solution obtained in a first passivation step as described in [0048],

[0117] Mn.sub.1 represents the manganese amount determined by ICP-OES in the first passivation step and thus here again on solution D.

[0118] (Mn/Fe).sub.deposited represents the ratio of the manganese content of the coating over the iron content of the coating determined by ICP-OES on the solution obtained by carrying out one passivation step as described above in [0048] on the corresponding half product before the wet wire drawing step.

[0119] Fe.sub.(i) represents the iron amount determined in dissolution step i and corresponds to the values determined by ICP-OES for the solutions D1 to D3, which may be added up in view of the formula above.

[0120] (Mn/Fe).sub.dissolution represents the ratio of Mn content over the content of Fe measured in a passivated or non-passivated environment (i.e. determined in a dissolution step carried out) on the bare substrate without coating and is determined for sample D as indicated in Table 4 below. Alternatively, (Mn/Fe).sub.dissolution can also be estimated based on steel composition of the steel substrate.

[0121] Mn.sub.(i) represents the manganese amount determined in passivation step i and corresponds to the values determined by ICP-OES for the solutions D1 to D3, which may be added up in view of the formula above.

[0122] Alternatively, Fe.sub.coating can also be determined as follows:

[00009]${\mathrm{Fe}}_{\mathrm{coating}}=\mathrm{Fe}1+\underset{i=2}{\overset{n}{.Math.}}\frac{\left[\left({\mathrm{Fe}}_{\left(i\right)}.Math.{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{dissolution}}\right)-{\mathrm{Mn}}_{\left(i\right)}\right]}{\left({\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{dissolution}}-{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{deposited}}\right)}$${\mathrm{Fe}}_{\mathrm{coating}}=0,92+\frac{\left[\left(2,61.113\%\right)-0,013\right]}{\left(0,60\%-0,07\%\right)}$$\text{.1000}/10\mathrm{to}\mathrm{get}\mathrm{mg}/\mathrm{kg}\left(g\mathrm{to}\mathrm{kg}\mathrm{and}100\mathrm{mL}\mathrm{solution}\right)$${\mathrm{Fe}}_{\mathrm{coating}}=143,0\mathrm{mg}/\mathrm{kg}$

[0123] Fe.sub.coating represents the iron content of the coating.

[0124] Fe.sub.1 represents the iron amount determined by ICP-OES in the first passivation step and thus here on solution D.

[0125] (Mn/Fe).sub.deposited represents the ratio of the manganese content of the coating over the iron content of the coating determined by ICP-OES on the solution obtained by carrying out one passivation step as described above in [0048] on the corresponding half product before the wet wire drawing step.

[0126] Fe.sub.(i) represents the iron amount determined in dissolution step i and corresponds to the values determined by ICP-OES for the solutions D1 to D3, which may be added up in view of the formula above.

[0127] (Mn/Fe).sub.dissolution represents the ratio of Mn content over the content of Fe measured in a passivated or non-passivated environment (i.e. determined in a dissolution step carried out) on the bare substrate without coating and is determined for sample D as indicated in Table 4 below. Alternatively, (Mn/Fe).sub.dissolution can also be estimated based on steel composition of the steel substrate.

[0128] Mn.sub.(i) represents the manganese amount determined in passivation step i and corresponds to the values determined by ICP-OES for the solutions D1 to D3, which may be added up in view of the formula above.

[0129] Whereby some of the ratios were estimated or determined as indicated in Table 4 below.

TABLE-US-00004 TABLE 4 Value Determined/Estimated [00010]${\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{steel}+\mathrm{brass}\mathrm{dissolution}}=0.83\%$ Estimated using Equation 4 below [00011]${\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{deposited}}=0.07\%$ Determined on the corresponding half product before the wet wire drawing step [00012]${\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{dissolution}}C=1.13\%$ Determined by ICP-OES on a solution obtained by carrying out a passivation step as per [0048] but on the bare steel substrate without coating [00013]${\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{dissolution}}D=0.60\%$ Determined by ICP-OES on a solution obtained by carrying out a corrosion step as per [0050] but on the bare steel substrate without coating after a passivation step as per [0048]

[00014]$\begin{array}{cc}{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{steel}+\mathrm{brass}\mathrm{dissolution}}=-0,001101+1,592{\left(\frac{\mathrm{Mn}}{\mathrm{Fe}}\right)}_{\mathrm{dissolution}}D& \mathrm{Equation}4\end{array}$

[0130] Equation 4 is thereby estimated based on a regression run on several values obtained by ICP-OES for solutions obtained by carrying at least two dissolution steps with at least one corrosion step on brass coating containing the same elements in same quantities as C and/or D (but without Fe) applied on steel substrates.