Chrome plating txheej txheem txheej txheem:
Cov txheej txheem chrome plating yog txheej txheem electrochemical, txheej txheem redox. Cov txheej txheem yooj yim yog raus rau hauv cov hlau ntsev tov raws li cov cathode, cov hlau ua cov anode, thiab tom qab txuas mus rau tam sim no, cov txheej hlau yuav muab tso rau ntawm qhov chaw. Schematic daim duab ntawm cov txheej txheem gravure electroplating: lub phaj roller yog cathode thiab titanium mesh yog anode.
Lub ntsiab Cheebtsam ntawm chromium tov Main ntsev:
Chromic anhydride Cov ntsiab lus: 200-260 g/L Catalyst: Sulfuric acid Cov ntsiab lus: 2.2-2.5 g/L Additives: Leveling thiab txhim kho efficiency Performance ntawm chromium plating txheej: Chromium yog silvery dawb hlau nrog ib me ntsis xiav tint, nrog ib tug txheeb ze atomic mass ntawm 51.99, ib tug ceev ntawm 6.98-7.21 g / cm3, thiab melting point ntawm 1875-1920 degree . Hlau chromium yog yooj yim passivated nyob rau hauv cov huab cua, tsim ib tug heev nyias passivation zaj duab xis nyob rau saum npoo.
1. Lub rotogravure chrome-plated txheej muaj ib tug heev hardness. Nyob ntawm seb muaj pes tsawg leeg ntawm cov tshuaj plating thiab cov txheej txheem, nws qhov nyuaj tuaj yeem sib txawv ntawm 400 txog 1200 HV.
2. Cov txheej chrome muaj cov cua sov zoo. Thaum tshav kub qis dua 500 degree, nws glossiness thiab hardness tsis hloov pauv loj.
3. Kev sib txhuam coefficient ntawm chrome-plated txheej, tshwj xeeb tshaj yog cov kev sib txhuam qhuav coefficient, yog qhov qis tshaj ntawm tag nrho cov hlau. Yog li ntawd, chrome-plated txheej muaj zoo hnav tsis kam.
4. Cov txheej txheej chrome-plated muaj cov tshuaj ruaj khov zoo thiab muaj cov tshuaj lom neeg ruaj khov hauv alkali, nitric acid, sulfide, carbonate thiab feem ntau cov pa roj thiab cov organic acids.
5. chrome-plated txheej yog yooj yim soluble nyob rau hauv hydrohalic acids (xws li hydrochloric acid) thiab kub concentrated sulfuric acid.
Chrome plating nta:
Chromic anhydride aqueous kua yog chromic acid, uas yog tib qhov chaw ntawm chromium plating. Txawm hais tias qhov ua tau zoo ntawm cov tshuaj plating muaj feem xyuam rau cov ntsiab lus chromic anhydride, nws feem ntau yog nyob ntawm cov kua qaub piv, uas yog, qhov sib piv ntawm chromic anhydride rau sulfuric acid.
1. Lub ntsiab tseem ceeb ntawm cov tshuaj chromium plating tsis yog hlau chromium ntsev, tab sis chromic acid, uas muaj oxygen-muaj kua qaub ntawm chromium, uas yog ib tug muaj zog acidic plating tov. Thaum lub sij hawm electroplating txheej txheem, cov txheej txheem cathode yog complex, thiab feem ntau ntawm cov cathode tam sim no tau noj nyob rau hauv ob sab kev xav: hydrogen evolution cov tshuaj tiv thaiv 2 thiab hexavalent chromium txo rau trivalent chromium cov tshuaj tiv thaiv 1. Yog li ntawd, cathode tam sim no efficiency ntawm chromium plating yog tsawg heev. (10% mus rau 18%). Kuj tseem muaj peb qhov tshwm sim txawv txav: 1. Kev ua haujlwm tam sim no txo qis nrog qhov nce ntawm chromic anhydride concentration; 2. Nws txo qis nrog qhov nce ntawm qhov kub thiab txias; 3. Nws nce nrog qhov nce ntawm qhov ceev tam sim no.
2. Hauv cov tshuaj chromium plating, ib qho nyiaj ntawm anions, xws li SO42-, yuav tsum tau muab ntxiv kom ua tiav qhov kev tso tawm ntawm cov hlau chromium.
3. Lub peev xwm dispersion ntawm cov tshuaj chromium plating yog tsawg heev. Rau qhov chaw nrog cov duab nyuaj, cov duab anodes lossis cov koom haum cathodes yuav tsum tau txais cov txheej txheem chromium plating. Cov kev cai rau hangers kuj tseem nruj.
4. Chromium plating yuav tsum muaj cov cathode tam sim no ntau dua, feem ntau yog siab dua 20A / dm2, uas yog ntau tshaj 10 npaug ntau dua li plating. Vim tias cov pa roj ntau tawm los ntawm cathode thiab anode, qhov kev tiv thaiv ntawm plating tov yog loj, lub tank voltage nce, thiab electroplating fais fab mov yuav tsum siab. Yuav tsum muaj lub zog hluav taws xob ntau dua 12V, thaum lwm hom plating tuaj yeem siv lub zog qis dua 8V.
5. Lub anode ntawm chromium plating tsis siv hlau chromium, vim hais tias chromium yog yooj yim heev rau yaj nyob rau hauv cov tshuaj plating, ua rau cov anode tam sim no efficiency ntau dua cov cathode efficiency, uas ua rau ib tug zuj zus noj ntawm chromic acid. Yog li ntawd, ib qho insoluble anode yog siv. Lead, txhuas-antimony alloy thiab txhuas-tin alloy feem ntau yog siv. Cov chromium noj hauv cov tshuaj plating yuav tsum tau ntxiv los ntawm kev ntxiv chromic anhydride.
6. Kev khiav hauj lwm kub ntawm chromium plating muaj qee yam dependence ntawm cathode tam sim no ceev. Kev hloov pauv kev sib raug zoo ntawm ob tuaj yeem tau txais cov xim chromium nrog cov khoom sib txawv. Txhawm rau txhawm rau ua kom lub zog sib txuas ntawm cov chromium plating txheej thiab cov substrate, cov phaj cov menyuam tuaj yeem preheated.
Lub cathode (cov menyuam nto) cov txheej txheem tshuaj tiv thaiv thaum lub sij hawm gravure chrome plating:
Cov tshuaj chrome plating feem ntau muaj nyob rau hauv daim ntawv ntawm chromic acid (CrO{0}}) thiab dichromic acid (Cr2O72-). Thaum tus nqi pH tsawg dua 1, (Cr2072- muaj 2 tus nqi tsis zoo thiab 7 oxygen atoms) raws li daim ntawv tseem ceeb; Thaum tus nqi pH yog 2-6, Cr2O72- thiab CrO{10}} muaj nyob rau hauv qhov sib npaug hauv qab no, uas yog, Cr2072- +H20===2CrO{{13} }H+. Nws tuaj yeem pom tau tias cov ions tam sim no hauv chrome plating electrolyte suav nrog Cr2O72-, H+, CrO{18}} thiab SO{19}}. Tsuas yog SO42-, lwm cov ions tuaj yeem koom nrog cov tshuaj tiv thaiv cathode. Plaub txheej txheem ntawm electrochemical tshuaj tiv thaiv ntawm cathode (cov menyuam nto):
Theem 1: Raws li cov electrode muaj peev xwm nce, qhov ceev tam sim no nce. Cov tshuaj tiv thaiv electrode yog 2H → H2 Reaction 2
Kauj Ruam 2: Raws li qhov muaj peev xwm electrode tseem nce ntxiv, qhov ceev tam sim no tig los txo qis. Qhov no yog txheej txheem ntawm kev tsim cov alkaline cathode zaj duab xis. (Qhov tsim ntawm alkaline cathode zaj duab xis yog vim kev noj ntau ntawm H + los ntawm ob qho kev cuam tshuam ①② ntawm lub cathode nto). Teb 1, Teb 2
Theem 3: Thaum lub peev xwm ntawm chromium nag lossis daus yog mus txog, chromium yog plated rau ntawm lub phaj roller nto. Raws li cov electrode muaj peev xwm nce ntxiv, qhov ceev tam sim no tig mus ntxiv. Cov tshuaj tiv thaiv electrode yog Cr6 → Cr 2H → H2 Reaction 1, Reaction 4
Cathodic zaj duab xis txoj kev xav thiab nws lub zog ntawm qhov zoo thaum lub sij hawm chrome plating:
Thaum lub sij hawm chromium plating txheej txheem, ib tug alkaline cathode zaj duab xis yog tsim nyob rau saum npoo ntawm lub phaj roller. Qhov kev sib cais no thawj zaug tshwm sim hauv zos thiab maj mam nthuav dav, yog li nthuav tawm thaj tsam me me ntawm lub substrate, qhov ceev tam sim no tiag tiag yog siab heev, thiab cov nyhuv polarization loj. Tsuas yog tom qab ntawd tuaj yeem chromium plating (mus txog chromium nag lossis daus muaj peev xwm) ua tiav ntawm qhov nrawm. Ib zaj duab xis colloidal yuav raug tsim nyob rau saum npoo ntawm txheej chromium tshiab, thiab kev sib cais thiab tiam ntawm cov yeeb yaj kiab colloidal yuav rov ua dua, ua lub luag haujlwm tseem ceeb ntawm kev tswj hwm.
Txawm hais tias SO42- nyob rau hauv cov tshuaj plating thiab trivalent chromium generated thaum lub sij hawm cathode txheej txheem tsis ncaj qha koom nyob rau hauv cov tshuaj tiv thaiv electrode, lawv muaj thiab cov ntsiab lus tseem ceeb heev rau qhov zoo ntawm chrome plating txheej.
1. Yog tias cov ntsiab lus ntawm trivalent chromium tsawg, cov zaj duab xis colloidal yog ib qho nyuaj rau tsim los yog nyias thiab ntxeem tau, thiab sulfuric acid tuaj yeem yaj nws yooj yim. Nyob rau lub sijhawm no, thaj chaw raug nthuav tawm yog qhov loj, thiab thaj chaw uas tsis tshua muaj tam sim no tsis tuaj yeem ncav cuag lub peev xwm los nag lossis daus ntawm chromium, yog li lub peev xwm npog chromium tsis zoo.
2. Yog hais tias trivalent chromium concentration siab, colloidal zaj duab xis yog tuab thiab ntom, thiab sulfuric acid yog ib qho nyuaj rau yaj. Cov txheej chromium tsuas tuaj yeem loj hlob ntawm thawj cov nplej, uas ua rau cov tawv nqaij crystallization thiab tsaus thiab npub txheej.
3. Cov ntsiab lus ntawm sulfuric acid yog siab, nws yog ib qho yooj yim rau yaj lub colloidal zaj duab xis, thiab tsis muaj chromium txheej nyob rau hauv qhov tsawg tam sim no ceev cheeb tsam, uas yog tib yam li cov xwm txheej thaum lub trivalent chromium yog tsawg. Yog tias sulfuric acid tsis txaus, cov chromium txheej yuav ntxhib, ib yam li qhov xwm txheej thaum trivalent chromium siab.
4. Yog li ntawd, lawv cov ntsiab lus yuav tsum nruj me ntsis tswj hauv chrome plating, tshwj xeeb tshaj yog qhov piv ntawm chromic anhydride rau sulfuric acid.
Kev cuam tshuam ntawm impurity ions hauv rotogravure chromium tov thiab kev tshem tawm:
Cov teeb meem tsis zoo hauv chromium plating electrolyte feem ntau suav nrog hlau, tooj liab, zinc, npib tsib xee, thiab lwm yam. Ntawm lawv, thaum twg cov hlau ion accumulates rau qee cov ntsiab lus, nws yuav ua rau muaj kev puas tsuaj rau cov txheej txheem chromium plating, xws li txo qhov ci ntau. ntawm cov txheej txheem, txo qhov muaj peev xwm dispersion ntawm electrolyte, thiab deterioration ntawm conductivity. Thaum cov hlau ion cov ntsiab lus hauv cov electrolyte siab, cov electrolyte yuav tsum tau kho. Kev kho mob uas tsis tshua muaj tam sim no tuaj yeem ua tiav qee qhov txiaj ntsig. Txawm li cas los xij, cov kua chromium yog corrosive heev, thiab qee qhov impurities yog yaj tom qab electrolysis. Thaum cov ntsiab lus ntawm cov hlau ions siab dhau lawm, kev sib pauv ion yog siv rau kev kho mob. Thaum kho, cov tshuaj chromium plating yog thawj zaug diluted kom cov ntsiab lus ntawm chromic acid tsis pub tshaj 120g / L, thiab tom qab ntawd txhaj rau hauv kem pauv. Cov tshuaj chromium plating kho nyob rau hauv txoj kev no tuaj yeem rov qab siv dua. Txhawm rau txuas ntxiv lub neej kev pab cuam ntawm cov resin, nws yog ib qho tsim nyog kom tsis txhob muaj kev sib cuag ncaj qha ntawm cov tshuaj chromium plating thiab cationic resin, thiaj li tiv thaiv cov resin los ntawm kev puas tsuaj los ntawm oxidation. Txoj kev sib pauv cation muaj tib yam cuam tshuam rau tooj liab ions thiab trivalent chromium, tab sis nws nyuaj thiab siv sijhawm.
Cov teebmeem ntawm trivalent chromium hauv gravure chromium tov thiab tshem tawm txoj kev:
Feem ntau, qhov nce ntawm trivalent chromium yog kho los ntawm electrolysis nrog ib tug loj anode thiab ib tug me me cathode. Yog tias cov ntsiab lus sulfuric acid siab, nws yog qhov zoo tshaj kom txo cov sulfuric acid kom zoo li qub ua ntej electrolysis. Cov sulfuric acid ntau dhau yuav cuam tshuam rau cov nyhuv electrolysis, ua rau nws nyuaj rau txo qis trivalent chromium. Feem ntau muaj ntau yam laj thawj rau kev nce ntawm trivalent chromium:
1. Qhov chaw anode me dhau. Qhov chaw anode yuav tsum yog 2-3 npaug ntawm thaj chaw cathode.
2. Cov ntsiab lus ntawm cov hlau impurities hauv cov tshuaj plating yog siab dhau.
3. Anode oxidation ua rau ib feem ntawm cov anode tsis yog conductive.
Taw qhia rau kev ua haujlwm ntawm gravure luam ntawv chromium mist inhibitor:
Thaum lub sij hawm chromium plating txheej txheem, vim yog siv cov insoluble anodes thiab tsawg cathode tam sim no efficiency, ib tug loj npaum li cas ntawm hydrogen thiab oxygen yog precipitated. Thaum cov roj khiav tawm ntawm cov kua dej, nws nqa ntau cov chromic acid, tsim chromium pos huab thiab ua rau muaj kuab paug loj. Tam sim no muaj ob txoj hauv kev los tua cov chromium pos huab.
1. Floating lub cev txoj kev: Muab ua npuas ncauj yas tej daim los yog fragments rau saum npoo ntawm cov tshuaj plating. Lub cev ntab no tuaj yeem thaiv kev khiav tawm ntawm chromium pos huab.
2. Ntxiv ua npuas ncauj inhibitor: Foam inhibitor yog ib qho surfactant uas tuaj yeem txo qhov nro ntawm cov txheej txheem plating thiab tsim cov npuas dej ruaj khov (zoo ib yam li cov dej ntxhua khaub ncaws ntxhua khaub ncaws, nrog cov npuas me me uas suav tsis txheeb rau saum npoo ntawm cov tshuaj plating).
Cov txheej ua npuas ncauj tsim los ntawm chromium mist inhibitor hauv cov txheej txheem plating nruj nreem npog cov txheej txheem plating. Thaum cov hydrogen thiab oxygen uas muaj chromic acid evaporate, lawv tuaj rau hauv kev sib cuag nrog cov npuas dej ntawm qhov chaw, thiab suav tsis txheeb cov chromic acid pos huab ua ke rau hauv cov tee loj. Vim yog cov nyhuv ntawm lub ntiajteb txawj nqus, lawv yuav rov qab mus rau cov tshuaj plating thaum lawv nce mus rau qhov siab, thaum cov hydrogen thiab oxygen txuas ntxiv mus kom txog thaum lawv tawm hauv cov kua dej, yog li ua tiav cov pa tawm thiab kev tawm tsam ntawm chromium pos huab.