Топло поцинковане превлаке пружају изванредну заштиту од корозије челичној подлози, али њена завршна обрада није увек глатка или уједначена каосликарство, прахомилисхерардизинг. Уопштено говорећи, поцинковани премази се одређују према дебљини цинкованог премаза за отпорност на корозију, а не по изгледу. Међутим, купац увек може да наведе шта су непотврдни{0}}изгледи, а испод су типични примери.
1. Заваривање прска шљака
Методе заваривања које не производе шљаку, као што је МИГ заваривање, су пожељније. Ако се користе обложене електроде за заваривање, све наслаге шљаке треба пажљиво уклонити са вара. Није могуће уклонити шљаку заваривања нормалним декапирањем, а сваки остатак изазива стварање црних тачака током врућег{0}}поцинковања. Прскање од заваривања, шљаке и поре увек треба уклонити пре него што почне предтретман галванизације, иначе ће површина галванизације изгледати веома грубо.
2. Замка киселине
Steel structures should be designed to avoid narrow crevices or gaps. If lap welds must be used, they should be welded around the entire joint. In case of double-sided fillet welds, the weld must be continued over the ends of the steel material to prevent the penetration of acid into any conceivable crevice. Plus, it is important to avoid the formation of pinholes. If the gap between contact surfaces is larger than 100 cm², venting holes must be provided to avoid the risk of explosion. Since molten zinc is more viscous than acid, it will seal the opening during hot-dip galvanizing. Afterwards, the acid will create holes in the coating, and then the rust-colored liquid will run on to the surface and spoils the appearance. Therefore, once acid has penetrated a crevice, it is impossible to be removed.
3.Дренажни шиљци
Drainage spike is a very common defect, and it can be greatly avoided by setting up a hanging angle close to 45 degree ,which can minimize drainage at the bottom of the workpiece. Hanging steel works with a horizontal angle is forbidden, which will cause excessive drainage spikes. Grinding of drainage spikes shall be handled carefully, and overgrinding shall be prohibited.
4. Дросс Пимплес
Dross pimples are small zinc-iron crystals formed from iron reacting with molten zinc during galvanization process. Dresses are heavier than zinc, and they settle on the bottom of the zinc kettle where they are periodically removed every 2 weeks or 10days. If the dross is stirred up and mixed into the molten zinc, it will often get trapped in the zinc coating leaving marks like pimples on the galvanization surface. An excessive amount of pimples can indicate a poor coating, and the zinc kettle shall be cleaned soon before another shift starts.
5. Бојење пепелом
Sometimes, ash is trapped inside areas and sticks to the outer side of the coating as the steelwork is lifted from the zinc bath. Ash may cause a light brown stain, a dull or dark surface appearance after removal. It has negative impact upon the performance of the galvanized coating, and it's possible to be repaired by zinc paint if its size is small.
6. Напрезање, грудвице и трчања
Избочине и линије дебље од оближњег поцинкованог премаза узроковане су различитим брзинама реакције цинка са површином челика због подручја напрезања на површини челика или присуства површина завара или метала шава са измењеном металургијом према основном металу. Ова појава се најчешће виђа на челичним цевима ичелични профили у ролни. There is no impact on coating performance, but it does have appearance issue. Please also be reminded that it's a bad practice to remove the lumps by angle grinder vigorously, and this could remove the whole zinc coating leaving the steel uncoated.
7. Хангинг Маркс
Hanging marks are almost impossible to avoid, but it's possible to adjust the hanging angle to minimize the hanging marks. And, it's also possible to use manual grinder to remove marks with care, and then repair them by zinc rich paint.
8.Галванизација љуштење
Flaking is the separation of the entire zinc coating, including the iron zinc alloy layers from the underlying steel. It is also known as delamination or chipping and should not be confused with peeling where only the top pure zinc layer separates from the underlying zinc alloy layers. Flaking usually occurs in thicker than normal galvanized coatings (200 μm or more), especially when these coatings receive impact forces during handling. Excessively thick coatings generate high stresses at the interface of the steel and galvanized coating which causes the zinc to become flaky and separate from the steel surface. Flaking typically occurs near the edges and creates bare spots in the protective zinc coating and it should be repaired to ensure ongoing corrosion protection. If the area of flaking is small, it can be repaired; however, if the flaking area is larger than allowed by the specifications, the part must be rejected and re-galvanized. Flaking can be avoided by minimizing the immersion time in the galvanizing kettle and cooling of the galvanized steel parts as quickly as possible, and if possible using a different steel grade. Steels with phosphorous content greater than 0.025 percent can experience flaking after galvanizing, even when the silicon levels are satisfactory.
9.Пеелинг анд Деламинатион
Delamination or peeling creates a rough coating on the steel where the zinc comes off. Many large galvanized structures and steel profiles take a long time to cool in the air, and the zinc coating continues to form zinc-iron layer after they have been lifted from the zinc bath. This continued coating formation leaves a gap between the top two layers of the galvanized coating. If there are many gaps formed, the top layer of zinc can separate from the rest of the coating and peel off the part. If the remaining coating still meets the minimum specification requirements, then the part is acceptable. If the zinc coating that remains on the steel does not meet the minimum specification requirements, then the part must be rejected and re-galvanized.
10.Голе тачке
Огољене тачке, непремазане површине на површини челика су површински дефект који може настати услед неадекватне припреме површине. Огољене тачке могу бити узроковане шљаком од заваривања, песком уграђеним у одливке, вишком алуминијума у котлу за поцинковање или уређајима за подизање који спречавају формирање премаза на малој површини. Да би се избегла гола места, галванизатор мора да обезбеди да су површине чисте и без рђе након претходног третмана. Мале голе тачке се могу поправити богатим спрејом цинка. Ако је величина голе тачке или укупан број тачака изнад захтева наведених у ИСО 1461, челични радни комад мора поново да прође целу претходну обраду и галванизацију.
11.Моттлинг
A mottled surface appearance is caused by uneven cooling rates of newly hot-dip galvanized articles after withdrawal from the zinc bath. During air cooling of the articles, the zinc-iron coating formation reaction, consuming the outer free zinc layer in the process, can continue for a short time as long as the steel stays about 550 Fahrenheit degree. Due to the fact that the galvanizing reaction continues on the interior portion and consumes the free zinc layer, but not the exterior potion of the steel, and this causes a nonuniform appearance of the zinc coating. However, this difference in appearance does not affect the corrosion protection of the galvanized coating, and this mottling surface is acceptable per ISO 1461 specifications. Therefore, to speed up the cooling process, quenching is recommended. But, the galvanizers shall be reminded that some designs might not be suitable for quenching as they have a tendency for warpage or distortion during quenching process.
After galvanizing, the steel cools from a temperature of approximately 840 F to ambient temperature. If the steel is quenched, cooling takes place rapidly, but not all galvanizers have quench baths and quenching is not recommended on some designs due to the potential for warpage/distortion of the steel. When the newly galvanized steel is allowed to cool naturally (without quenching), it can take several hours for the steel to come down to ambient temperature. Thinner steel cools faster while thicker steel takes longer to cool. Sometimes an individual piece of steel will have different cooling rates.
12.Дулл Финисх
The most common reason for dull appearances is the chemistry of the workpiece, and the main elements of steel chemistry which most strongly influence the final appearance are silicon and phosphorous. Both elements are catalysts to coating growth, and the thicker coating is responsible for the differing appearance. In addition to producing thicker coatings, highly reactive steels tend to have a matte gray or mottled appearance instead of a typical bright coating.
13. Лоша поправка галванизације
Радови на поправци галванизације су на неки начин једнако важни као и сами радови на галванизацији и постоји неколико уобичајених грешака које треба избећи.
√ Overgrinding, removed the zinc coating completely
√ Употреба распршивача са малим садржајем цинка за поправку
√ Дебљина поправке цинка не задовољава потребну дебљину
Фабманн има строгу контролу процеса производње на месту покривањаповршинска обрада метала, и имамо веома искусне инжењере квалитета који имају дубоко знање о предтретману топлог поцинчавања, галванизацији и поправци галванизације. Због тога можемо да обезбедимо врхунски квалитет за широк спектар челичних производа као што сухардвер носача прикључне станице, прилагођени регали, ојачани угаони носачи, челични профили у ролни, заграде за знаковеикавезни носачи за узгој рибе to our clients.
