proceso por inmersion en caliente nov 2015 parte 1

8/16/2019 Proceso Por Inmersion en Caliente Nov 2015 Parte 1

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PROCESO POR INMERSION EN CALIENTEPROCESO POR INMERSION EN CALIENTE


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PROCESO POR INMERSION ENPROCESO POR INMERSION EN

CALIENTECALIENTE

• Hot dip galvanizing Molten zinc

• Degreasing Hot caustic

• Pickling Hydrochloric acid

• Pre-fluxing Zinc am. chloride

• Quenching Dichromate

• Loading - jigging


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CALIENTECALIENTELoading - jigging

The steel items need to be supported during the hot dipgalvanizing process.

Can the item be easily jigged?Will touch marks be a problem?

Solutions and molten zinc must be able to flow into allsections and drain off all sections.

Steel items must be designed to prevent air, solutions andmolten zinc becoming trapped

Check design for possible problems


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CALIENTECALIENTEDegreasing

A hot (90oC) caustic bath is used to remove -Oil, grease, paint another organic compounds

If these contaminating materials are not removed, the nextstage of the process (pickling) is affected

Check if any paint is on item - some paints are not easilyremoved and may require abrasive blasting before

galvanizing

Some pipes and pipe fittings have a black varnish coatingthat cannot be removed in the caustic bath.


10/42El baño alcalino caliente para desengrase


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CALIENTECALIENTE

Acid pickling

The steel items are immersed in hydrochloric acid toremove - rust, mill scale and other metal oxides

The steel surface must be perfectly clean of these oxidesfor the molten zinc to react with the steel

Very heavy rust may not be easily removed by pickling -badly rusted items should be abrasive blasted ormechanically cleaned first.


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El Tanque de Decapado


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CALIENTECALIENTE

Pre-fluxing

Steel items are water rinsed after pickling and immersed inhot (70-80oC) zinc ammonium chloride (ZAC) solution.

The ZAC solution conditions the clean steel surface readyfor hot dip galvanizing.

Good pre-treatment = good quality galvanizing


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CALIENTECALIENTE


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CALIENTECALIENTE


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Al galvanizar el acero,

se interrelacionan el zinc

y el hierro formándose

capas con diferenteconcentración de los

metales.


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La rotación a gran velocidad permite que

se desprendan los residuos de Zinc,

mejorando el acabado y garantizando el

correcto desempeo de la cuerda.


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CALIENTECALIENTEQuenchingAfter hot dip galvanized steel item is removed from thegalvanizing bath, it is immediately quenched in a sodiumdichromate solution

The dichromate quenching cools the item so that it can bequickly handled and conditions the surface of the

galvanized coating to maintain its bright appearance.

Chromate quenching will reduce white rusting problems.White rust forms when rainwater reacts with newly

galvanized steel to form zinc hydroxide.

Poor storage or HDG steel will also promote white rust.


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CALIENTECALIENTEHot dip galvanizing

The steel is immersed in molten zinc (temp 4500C)

The clean steel surface reacts with the molten zinc to form azinc-iron alloy which is very strongly bonded to the surface.

The hot dip galvanized coating forms in 3-5 minutes,depending on the steel thickness.

Galvanized coating

Steel

Free zinc layer

Micrograph - 100 X

Alloy layers


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CALIENTECALIENTECharacteristics• Typically 65 - 150 microns thick (1 mm = 1000 microns)

• Zinc iron alloy layers make up 80% - 100% of the coating.

• The zinc-iron alloy layers are harder than 250 grade steel

Steel

Zinc-iron alloys

Zinc

Micrograph of hot dip galvanized coating



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GALVANIZADO EN CONTINUOGALVANIZADO EN CONTINUO



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%inc en la In"raestructura


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%inc en la In"raestructura!l Zinc prolonga en forma significativa la duración de los

productos de acero y las inversiones de capital tales como "asas Automóviles

#uentes $elecomunicaciones y transporte.

!stadios %nstalaciones portuarias &edes de electricidad y de distribución de agua


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&arras

Mallas

'erra(es ) a!arras

Productos de refuerzo galvanizados

proceso por inmersion en caliente nov 2015 parte 1

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