電泳加工油漆的角落腐蝕試驗方法。這種測試方法是用切紙刀片模擬車身邊角,在刀片磷化後用電泳法檢測電泳漆的邊角附著力。將符合要求的切紙刀片除油、酸洗、磷化後,選擇磷化處理好、晶體一致的切紙刀片進行電泳。
電泳加工小時時,注意刃口外殼朝向電梯間的一側,使刀盤上有凹槽的外殼一側朝向同一方向。電泳時,保證極比為1∶2,在符合規範的前提下,將清洗幹淨的刀頭烘幹,保證漆層厚度在標準範圍內。將刃口向上放入鹽霧箱內,與垂直麵成15° ~ 30°角。根據GB/T10125—1997,進行168h中性鹽霧試驗,判斷浸蝕情況。讓三個刀頭相互平行,取實驗結果的算術平均值。電泳和頂部加熱幹燥過程中塗層厚度變化:頂(ding)部(bu)表(biao)層(ceng)折(zhe)射(she)率(lv)高(gao),電(dian)泳(yong)時(shi)頂(ding)部(bu)充(chong)放(fang)電(dian)條(tiao)件(jian)導(dao)致(zhi)電(dian)流(liu)強(qiang)度(du)相(xiang)對(dui)較(jiao)高(gao)。隨(sui)著(zhe)整(zheng)個(ge)電(dian)泳(yong)過(guo)程(cheng)的(de)發(fa)展(zhan),漆(qi)層(ceng)逐(zhu)漸(jian)變(bian)厚(hou),電(dian)阻(zu)膨(peng)脹(zhang),絕(jue)緣(yuan)層(ceng)水(shui)平(ping)上(shang)升(sheng),這(zhe)部(bu)分(fen)電(dian)流(liu)強(qiang)度(du)緩(huan)慢(man)下(xia)降(jiang),然(ran)後(hou)電(dian)沉(chen)積(ji)到(dao)鄰(lin)近(jin)區(qu)域(yu)。塗(tu)層(ceng)的(de)固(gu)體(ti)成(cheng)分(fen)集(ji)中(zhong)在(zai)頂(ding)部(bu),邊(bian)角(jiao)粘(zhan)合(he)。然(ran)而(er),烘(hong)烤(kao)後(hou),表(biao)麵(mian)塗(tu)層(ceng)的(de)厚(hou)度(du)顯(xian)著(zhu)降(jiang)低(di)。這(zhe)也(ye)是(shi)由(you)表(biao)麵(mian)張(zhang)力(li)的(de)變(bian)化(hua)引(yin)起(qi)的(de)。與(yu)表(biao)麵(mian)張(zhang)力(li)的(de)危(wei)害(hai)相(xiang)比(bi),作(zuo)用(yong)力(li)對(dui)塗(tu)層(ceng)加(jia)熱(re)幹(gan)燥(zao)的(de)幹(gan)擾(rao)可(ke)以(yi)忽(hu)略(lve)不(bu)計(ji)。
頂(ding)部(bu)的(de)金(jin)屬(shu)材(cai)料(liao)特(te)別(bie)薄(bo),環(huan)境(jing)溫(wen)度(du)上(shang)升(sheng)比(bi)其(qi)他(ta)部(bu)分(fen)快(kuai)。這(zhe)部(bu)分(fen)底(di)部(bu)的(de)建(jian)築(zhu)塗(tu)料(liao)環(huan)境(jing)溫(wen)度(du)迅(xun)速(su)上(shang)升(sheng),產(chan)生(sheng)熱(re)對(dui)流(liu),底(di)部(bu)的(de)原(yuan)材(cai)料(liao)從(cong)底(di)部(bu)向(xiang)上(shang)轉(zhuan)移(yi)到(dao)終(zhong)點(dian)。表(biao)麵(mian)張(zhang)力(li)隨(sui)著(zhe)環(huan)境(jing)溫(wen)度(du)的(de)升(sheng)高(gao)而(er)降(jiang)低(di)。到(dao)達(da)終(zhong)點(dian)的(de)原(yuan)料(liao)表(biao)麵(mian)張(zhang)力(li)與(yu)周(zhou)圍(wei)原(yuan)料(liao)相(xiang)比(bi)很(hen)低(di),周(zhou)圍(wei)原(yuan)料(liao)對(dui)終(zhong)點(dian)原(yuan)料(liao)兩(liang)側(ce)造(zao)成(cheng)縱(zong)向(xiang)外(wai)力(li)。結(jie)論(lun)導(dao)致(zhi)這(zhe)裏(li)的(de)原(yuan)料(liao)向(xiang)外(wai)流(liu)動(dong),反(fan)過(guo)來(lai)推(tui)動(dong)一(yi)部(bu)分(fen)原(yuan)料(liao)一(yi)起(qi)轉(zhuan)移(yi)。同(tong)時(shi),底(di)部(bu)被(bei)加(jia)熱(re)的(de)溫(wen)熱(re)液(ye)體(ti)再(zai)次(ci)上(shang)升(sheng)到(dao)表(biao)層(ceng),加(jia)強(qiang)了(le)的(de)流(liu)動(dong)性(xing)。這(zhe)樣(yang)一(yi)來(lai),流(liu)動(dong)性(xing)差(cha)的(de)液(ye)層(ceng)越(yue)來(lai)越(yue)不(bu)穩(wen)定(ding),頂(ding)塗(tu)層(ceng)慢(man)慢(man)向(xiang)兩(liang)邊(bian)移(yi)動(dong),變(bian)軟(ruan)。頂(ding)部(bu)生(sheng)鏽(xiu)的(de)根(gen)本(ben)原(yuan)因(yin):頂(ding)部(bu)過(guo)早(zao)生(sheng)鏽(xiu)可(ke)能(neng)是(shi)由(you)於(yu)頂(ding)部(bu)磷(lin)化(hua)處(chu)理(li)不(bu)好(hao)或(huo)塗(tu)層(ceng)缺(que)陷(xian)造(zao)成(cheng)的(de)。在(zai)塗(tu)料(liao)配(pei)方(fang)中(zhong),如(ru)果(guo)幹(gan)固(gu)析(xi)出(chu)的(de)組(zu)分(fen)表(biao)麵(mian)張(zhang)力(li)不(bu)匹(pi)配(pei),很(hen)可(ke)能(neng)會(hui)造(zao)成(cheng)縮(suo)孔(kong)。在(zai)加(jia)熱(re)和(he)幹(gan)燥(zao)的(de)過(guo)程(cheng)中(zhong),頂(ding)部(bu)的(de)塗(tu)層(ceng)具(ju)有(you)流(liu)動(dong)性(xing)和(he)遷(qian)移(yi)性(xing)。塗(tu)層(ceng)內(nei)部(bu)結(jie)構(gou)中(zhong)表(biao)麵(mian)張(zhang)力(li)低(di)的(de)組(zu)分(fen)向(xiang)表(biao)層(ceng)移(yi)動(dong),周(zhou)圍(wei)化(hua)學(xue)品(pin)表(biao)麵(mian)張(zhang)力(li)高(gao),所(suo)以(yi)原(yuan)料(liao)會(hui)從(cong)低(di)表(biao)麵(mian)張(zhang)力(li)區(qu)向(xiang)高(gao)表(biao)麵(mian)張(zhang)力(li)區(qu)移(yi)動(dong),產(chan)生(sheng)縮(suo)孔(kong)。塗(tu)層(ceng)中(zhong)幾(ji)乎(hu)沒(mei)有(you)有(you)機(ji)溶(rong)劑(ji)。現(xian)在(zai)廣(guang)泛(fan)使(shi)用(yong)第(di)六(liu)代(dai)陰(yin)極(ji)電(dian)泳(yong)建(jian)築(zhu)塗(tu)料(liao),塗(tu)層(ceng)發(fa)熱(re)降(jiang)低(di)10%左zuo右you。有you機ji溶rong劑ji的de蒸zheng發fa引yin起qi塗tu層ceng表biao麵mian張zhang力li梯ti度du方fang向xiang的de微wei小xiao變bian化hua,這zhe對dui頂ding部bu塗tu層ceng的de軟ruan化hua和he收shou縮suo具ju有you有you限xian的de直zhi接jie影ying響xiang。提ti高gao電dian泳yong漆qi邊bian角jiao附fu著zhe力li的de方fang法fa:縮孔整個過程是一個漫長的過程。如果管理係統的粘度不大,管理係統可以快速完成油漆而不收縮;如果管理體係粘度很高,原材料流動性慢,縮孔的可能性也小;隻有粘度稍低,才有可能出現這種縮孔。
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