Background technology
Chromium coating has good hardness, wear resistance, solidity to corrosion and decorative appearance, and it is not only for decorative coating, also in a large number for functional coating.At present, chromium plating has become one of most widely used plating in electroplating industry.For a long time, chromium plating adopts hexavalent chromium plating technique, and sexavalent chrome toxicity is large, is carcinogenic substance.And chromic toxicity is very low, be only biological action and the Pollution abatement [J] of chromic 1%(chromium. Industrial and Commercial University Of Chongqing's journal (natural science edition), 2004,21 (4): 325-328. author: Jiang Lan, Wang little Lan); Adopt trivalent chromium to replace hexavalent chromium plating chromium to compare, there are a lot of excellent specific properties.
At present, trivalent chromium plating chromium process industrialization not yet comprehensively.Especially trivalent chromium plating hard chrome or hard chromium technique are still in development.Conventionally utilize DC electrodeposition trivalent chromium coating, generally only can obtain the coating of several micron thickness.The reason that Electrodeposition of Trivalent Chromium can not thicken is because the cathode characteristic of Electrodeposition of Trivalent Chromium determines, prolongation along with electrodeposition time, bath pH value rises gradually, finally substantially reach a stationary value, near the mensuration [J] of pH value negative electrode during for 8.4-8.6(trivalent chromium plating. electroplate and environmental protection 1984, (5): 21-25, author: Tu Zhenmi, Yang Zhelong, Wang Canghai etc.).When pH value surpasses 8, will generate ol bridge polymkeric substance or Cr (OH)
3colloid; thereby hindered the continuation deposition of trivalent chromium coating; affected normally carrying out of chromium coating crystallization; cause coating to be difficult to continue to thicken, this be the trivalent chromium plating key point that can not thicken (reason that the research-coating of trivalent chromium plating mechanism can not thicken [J]. material protection, 1985; (3): 13-17; author: Tu Zhenmi, Yang Zhelong, Wang Canghai etc.).
The plating hard chromium technique that Chinese patent " a kind of full-sulfate trivalent-chromium solution for plating thick chromium and electro-plating method " (patent publication No. CN 101643924) has proposed to improve by flow of solution, can obtain the amorphous chromium coating of 30-50 μ m.US Patent No. P 20080169199 discloses a kind of trivalent chromium plating solution, although thickness of coating reaches 50 μ m left and right, does not have to propose to strengthen the additive that plating solution continues throwing power.Adopt in addition the measures such as the pulse power also can suitably increase the thickness of chromium coating, but the ability that plating solution continues to electroplate has still been subject to serious restriction.
Summary of the invention
Technical problem to be solved by this invention is to provide a kind of additive for trivalent chromium plating hard chromium electrolytic solution and electrolyte quota method, this additive forms simply, formula is reasonable, can effectively extend the trivalent chromium plating time, increase chromium coating thickness, utilize present method to overcome the defect of traditional trivalent chromium plating hard chromium plating process, increase thickness of coating, improve plating solution and continue the ability of electroplating.
For solving the problems of the technologies described above, the present invention is the aqueous solution that adopts deionized water preparation for the additive of trivalent chromium plating hard chromium electrolytic solution, the described aqueous solution comprises at least one light metal compound and at least one organic carboxyl acid or carboxylate salt, the concentration of described light metal compound in the aqueous solution is 80 ~ 900 g/L or 60 ~ 600 g/L, and described organic carboxyl acid or the carboxylate salt concentration in the aqueous solution is 30 ~ 500 g/L.
Further, above-mentioned light metal compound is vitriol, muriate or vitriol and the muriatic mixture of light metal, and light metal is one or both in titanium, aluminium, magnesium.
Further, above-mentioned organic carboxyl acid or carboxylate salt are tartrate, tartrate, citric acid, Citrate trianion, oxysuccinic acid, malate, oxalic acid, oxalate, lactic acid, Lactated two or more composition.
Adopt the electrolyte quota method of described additive to comprise the steps:
Step 1, employing deionized water obtained aqueous solution additive, deionized water temperature is elevated to 90 ℃, under stirring, add light metal compound and organic carboxyl acid or carboxylate salt, after stirring and dissolving, 80 ℃ of ageing 5-10 h are stand-by, wherein, organic carboxyl acid or the carboxylate salt concentration in the aqueous solution is 30 ~ 500 g/L, in sulfate system electrolytic solution, the concentration of light metal compound in the aqueous solution is 80 ~ 900 g/L, in chloride system electrolytic solution, the concentration of light metal compound in the aqueous solution is 60 ~ 600 g/L;
Step 2, according to the volume number of the trivalent chromium plating hard chromium electrolytic solution of need preparation, the deionized water that adds half volume in trivalent chromium chrome plating groove, concentration 150 ~ 200 g/L according to chromium sulphate in trivalent chromium plating hard chromium electrolytic solution or chromium chloride concentration 160 ~ 213 g/L in trivalent chromium plating hard chromium electrolytic solution, chromium sulphate or chromium chloride are added under whipped state, concentration 76 ~ 100 g/L in trivalent chromium plating hard chromium electrolytic solution according to formic acid or formate, formic acid or formate are added and be stirred to completely and dissolve, concentration 20 ~ 50 g/L according to boric acid in trivalent chromium plating hard chromium electrolytic solution, concentration 100 ~ 120 g/L in trivalent chromium plating hard chromium electrolytic solution according to conducting salt potassium sulfate or Repone K, add boric acid and conducting salt potassium sulfate or Repone K, be stirred to completely and dissolve, then according to additive, the concentration in trivalent chromium plating hard chromium electrolytic solution is 100 ~ 200 ml/L, add additive, supplement deionized water to the electrolyte product that needs preparation, 40 ℃ of ageing 24 h, use NaOH solution, dilute sulphuric acid or dilute hydrochloric acid are adjusted electrolyte ph to 1 ~ 3, can electroplate.
The additive and the electrolyte quota method that due to the present invention, are used for trivalent chromium plating hard chromium electrolytic solution have adopted technique scheme, be that additive adopts deionized water obtained aqueous solution, the aqueous solution comprises at least one light metal compound and at least one organic carboxyl acid or carboxylate salt, the concentration of light metal compound is 80 ~ 900 g/L or 60 ~ 600 g/L, and the concentration of organic carboxyl acid or carboxylate salt is 30 ~ 500 g/L.Deionized water temperature is elevated to 90 ℃, under stirring, add light metal compound and organic carboxyl acid or carboxylate salt, after stirring and dissolving, 80 ℃ of ageing 5-10 h are mixed with additive, according to the volume number of the electrolytic solution of need preparation, in coating bath, add half deionized water, according to certain concentration, add chromium sulphate or chromium chloride, formic acid or formate, boric acid, conducting salt potassium sulfate or Repone K, additive, supplement deionized water to the electrolyte product that needs preparation, 40 ℃ of ageing 24 h make electrolytic solution, use NaOH solution, dilute sulphuric acid or dilute hydrochloric acid are adjusted electrolyte ph to 1 ~ 3, can electroplate.This additive forms simply, formula is reasonable, can effectively extend the trivalent chromium plating time, increase chromium coating thickness, utilizes present method to overcome the defect of traditional trivalent chromium plating hard chromium plating process, increases thickness of coating, and raising plating solution continues the ability of plating.
Embodiment
The present invention is the aqueous solution that adopts deionized water preparation for the additive of trivalent chromium plating hard chromium electrolytic solution, the described aqueous solution comprises at least one light metal compound and at least one organic carboxyl acid or carboxylate salt, the concentration of described light metal compound in the aqueous solution is 80 ~ 900 g/L or 60 ~ 600 g/L, and described organic carboxyl acid or the carboxylate salt concentration in the aqueous solution is 30 ~ 500 g/L.
Further, above-mentioned light metal compound is vitriol, muriate or vitriol and the muriatic mixture of light metal, and light metal is one or both in titanium, aluminium, magnesium.
Further, above-mentioned organic carboxyl acid or carboxylate salt are tartrate, tartrate, citric acid, Citrate trianion, oxysuccinic acid, malate, oxalic acid, oxalate, lactic acid, Lactated two or more composition.
Adopt the electrolyte quota method of described additive to comprise the steps:
Step 1, employing deionized water obtained aqueous solution additive, deionized water temperature is elevated to 90 ℃, under stirring, add light metal compound and organic carboxyl acid or carboxylate salt, after stirring and dissolving, 80 ℃ of ageing 5-10 h are stand-by, wherein, organic carboxyl acid or the carboxylate salt concentration in the aqueous solution is 30 ~ 500 g/L, in sulfate system electrolytic solution, the concentration of light metal compound in the aqueous solution is 80 ~ 900 g/L, in chloride system electrolytic solution, the concentration of light metal compound in the aqueous solution is 60 ~ 600 g/L;
Step 2, according to the volume number of the trivalent chromium plating hard chromium electrolytic solution of need preparation, the deionized water that adds half volume in trivalent chromium chrome plating groove, concentration 150 ~ 200 g/L according to chromium sulphate in trivalent chromium plating hard chromium electrolytic solution or chromium chloride concentration 160 ~ 213 g/L in trivalent chromium plating hard chromium electrolytic solution, chromium sulphate or chromium chloride are added under whipped state, concentration 76 ~ 100 g/L in trivalent chromium plating hard chromium electrolytic solution according to formic acid or formate, formic acid or formate are added and be stirred to completely and dissolve, concentration 20 ~ 50 g/L according to boric acid in trivalent chromium plating hard chromium electrolytic solution, concentration 100 ~ 120 g/L in trivalent chromium plating hard chromium electrolytic solution according to conducting salt potassium sulfate or Repone K, add boric acid and conducting salt potassium sulfate or Repone K, be stirred to completely and dissolve, then according to additive, the concentration in trivalent chromium plating hard chromium electrolytic solution is 100 ~ 200 ml/L, add additive, supplement deionized water to the electrolyte product that needs preparation, 40 ℃ of ageing 24 h, use NaOH solution, dilute sulphuric acid or dilute hydrochloric acid are adjusted electrolyte ph to 1 ~ 3, can electroplate.
The present invention has overcome the defect of prior art, and the additive providing forms simply, formula is reasonable, can effectively extend the trivalent chromium plating time, increase chromium coating thickness.This additive only need be used in conjunction with chromic salt, formate, sodium salt and boric acid etc., just can carry out easily trivalent chromium plating hard chromium.Use the trivalent chromium chrome plating electrolytic solution containing this additive, in trivalent chromium plating technique, coating being thickened to Performance Detection shows, under identical electroplating technical conditions (current density, pH value, temperature), sustainable plating 1 ~ 5 h, thickness of coating can reach 20 ~ 100 μ m, and coating hardness is 650 ~ 750 Hv.And binding force of cladding material is good, bright appearance.
Below by following specific embodiment, the present invention is further explained.
Embodiment 1: additive preparation, get 500 ml deionized waters, and be heated 90 ℃, add MgCl
2380g, is stirred to dissolving, then adds H in solution
8c
6o
7390g, stirs it is dissolved, and adds deionized water to 1 L, and sealing 80 ℃, to place 5 h stand-by; Get 400 ml deionized waters, add successively CrCl
36H
2o 213 g, ammonium formiate 76 g, boric acid 40 g, sodium-chlor 100 g, stir it dissolved completely, and 100 ml additives are added wherein; Add deionized water to 1L, place ageing 24h for 40 ℃; Use front by electroplate liquid pH regulator to 2; To electroplate after test piece polishing, activation, washing at 15 A/dm
2current density under electroplate 1 h, can obtain the white bright coating that 28 μ m are thick, electrolytic solution stability can reach 200 Ah/L.
Embodiment 2: additive preparation, get 500 ml deionized waters, and be heated 90 ℃, add MgCl
2190g, is stirred to dissolving, then adds H in solution
2c
2o
2250g, stirs it is dissolved, and adds deionized water to 1L, and sealing 80 ℃, to place 5h stand-by; Get 400 ml deionized waters, after stirring and dissolving, add successively CrCl
36H
2o213 g, ammonium formiate 76 g, boric acid 40 g, Repone K 100 g, add 200 ml additives wherein; Add deionized water to 1L, place ageing 24h for 40 ℃; Use front by electroplate liquid pH regulator to 2; To electroplate after test piece polishing, activation, washing at 15 A/dm
2current density under electroplate 2.5 h, can obtain the white bright coating that 55 μ m are thick, electrolytic solution stability can reach 180 Ah/L.
Embodiment 3: additive preparation, get 500 ml deionized waters, and be heated 90 ℃, add Al
2(SO
4)
3420 g, are stirred to dissolving, then add H in solution
8c
6o
7240 g, stir it are dissolved, and add deionized water to 1L, and sealing 80 ℃, to place 5h stand-by; Get 400 ml deionized waters, after stirring and dissolving, add successively Cr
2(SO
4)
36H
2o 250 g, formic acid 32g, boric acid 60 g, potassium sulfate 100g, sodium sulfate 100g, add 160 ml additives wherein; Add deionized water to 1L, place ageing 24h for 40 ℃; Use front by electroplate liquid pH regulator to 2; To electroplate after test piece polishing, activation, washing at 20 A/dm
2current density under electroplate, continuous electroplating 3 h can obtain the white bright coating that 80 μ m are thick, electrolytic solution stability can reach 100 Ah/L.
Embodiment 4: additive preparation, get 500 ml deionized waters, and be heated 90 ℃, add TiCl
3400 g, are stirred to dissolving, then add H in solution
6c
3o
3160g, stirs it is dissolved, and adds deionized water to 1L, and sealing 80 ℃, to place 5h stand-by; Get 400ml deionized water, after stirring and dissolving, add successively CrCl
36H
2o 213 g, ammonium formiate 76 g, boric acid 40 g, Repone K 80 g, sodium-chlor 80 g, add 100 ml additives wherein; Add deionized water to 1L, place ageing 24h for 40 ℃; Use front by electroplate liquid pH regulator to 2; To electroplate after test piece polishing, activation, washing at 15 A/dm
2current density under electroplate, it is the white bright coating that 100 μ m are thick that continuous electroplating 5 h can obtain thickness, electrolytic solution stability can reach 150 Ah/L.