amol-cold galvanizing quations

8/20/2019 Amol-Cold Galvanizing Quations

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Cold Galvanizing Questions

Q. 1.What exactly is Cold galvanizing?

A. Cold galvanisation is an organic, single-component zinc coating of minimum !"#$eight% zinc in the dry layer.

Q. !.&s it a 'aint?

A. (o, it gives the same cathodic protection as hot dip galvanizing, )ut it is applied

as a paint.

Q. *. +oes it have to )e mixed $ith other products?

A. (o, the cold galvanisation product is a single component. &t reuires no mixing

$ith other chemicals to mae it cure.

Q. .&f it is not a paint, $hat can it )e compared to?

A. &t can )e compared $ith hot-dip galvanizing, although, $eight for $eight, it out-

lasts hot-dip.

Q. /.0o$ is it not a paint if it is a liuid?

A. Cold galvanizing is applied as a paint )ut does not )ehave liea paint e.g. it does

not sin over2 in the tin, it does not clogup spray-gun nozzles, it does not form loose

runs2 easily, it does not go )lotchy2 in damp conditions, and it does not go onto

surfaces and remain $et lie paint does. &t also does not go on tacy2 lie paint.

Q. 3.+oes cold galvanising give the same lifetime

A. 4es, it does give the same lifetime expectation as hot dip galvanising. &t last even

* times longer under $ater.

Q. 5.+oes Cold 6alvanising contain the same solvents as paints?

A. (o, the cold galvanising product 7ust-Anode is a natural

solvent extracted from citrus fruit #orange peelings%. &t even smells lie orange. Q.

8.+oes this natural solvent contain toxic solvents used in paint?

A. (o, the cold galvanising product 7ust-Anode does not contain any organic

solvent such as xylene, )enzene, toluene, )utyl acetone, methylene-chloride nor

9:; methyl-ethyletone regularly used for the fa)rication of normal paint.


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Q. .0o$ does cold galvanizing $or?

A. .

Q. 1=.What if the cold galvanizing layer is scratched through to the )are metal?

A.


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A.


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galvanisation can therefore )e used as shop and $elding primer and later on

increased to a full 8=@m cathodic protection.

Q. !.Can $e use cold galvanisation on a $et surface?

A. 4es, after 0igh 'ressure $ater Iet cleaning you can apply cold galvanisation

$ithout the need for complete drying of the surface.

Q. !/.+o $e have to $et the surface #$ith fresh $ater% of a freshly applied cold

galvanisation?

A. (o, you donDt have to do so. &t certainly gives a good result, )ecause it improves

the polymerisation and the formation of zinc salts and zinc car)onates on the

surface and this oEers a )arrier protection $ith a harder coating. &t also helps toavoid dar spots on the freshly coated surface due to raindrops.

Q. !3.What is the most economical $ay of preparing large steel surfaces #e.g.

ships%?

A.


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Q. *=.What is the diEerence )et$een the traditional zinc silicate paint and cold

galvanisation?

A. Jn top of the uality diEerence )et$een a paint and a cathodic protection there

are a num)er of practical diEerences. Mn-i is a t$o-component productG cold galva

is a single-component. Mn-i reuire a a * standard of cleanliness, cold galvareuires only a !./.


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A. icers, zinc #and cold galva% is a)out

5=>icers and the hot-dip layer alloy has a delta layer of 1=@m $ith a hardness of

a)out !=>icers.


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saline/zinc solution with a zinc anode and steel conductor. Zinc electroplating maintains a dominant

position among other electroplating process options, based upon electroplated tonnage per annum.

According to the International Zinc Association, more than million tons are used yearly for both !ot "ip

#alvanizing and $lectroplating.%&' The (lating of Zinc was developed at the beginning of the )*th century.

At that time, the electrolyte was cyanide based. A significant innovation occurred in the +*s, with the

introduction of the first acid chloride based electrolyte.%)' The -*s saw a return to alaline electrolytes,only this time, without the use of cyanide. ompared to hot dip galvanizing, electroplated zinc offers these

significant advantages0

• 1ower thicness deposits to achieve comparable performance

• 2roader conversion coating availability for increased performance and color options

• 2righter, more aesthetically appealing, deposits

• !istory %edit'

•Zinc plating was developed and continues to evolve, to meet the most challenging corrosionprotection, temperature and wear resistance re3uirements. $lectroplating of zinc was invented in

&-** but the first bright deposits were not obtained until the early &45*s with the alaline cyanide

electrolyte. 6uch later, in &4++, the use of acid chloride baths improved the brightness even

greater. The latest modern development occurred in the -*s, with the new generation of alaline,

cyanide7free zinc. 8ecent $uropean 9nion directives :$1;/8o!%5' prohibit automotive,

other original e3uipment manufacturers :?$6> and electrical and electronic e3uipment

manufacturers from using he@avalent chromium :r;I>. These directives combined with increased

performance re3uirements by the ?$6, has led to an increase in the use of alaline zinc, zinc

alloys and high performance trivalent passivate conversion coatings.

• (rocesses %edit'

• The corrosion protection afforded by the electrodeposited zinc layer is primarily due to the anodic

potential dissolution of zinc versus iron :the substrate in most cases>. Zinc acts as a sacrificial

anode for protecting the iron :steel>. =hile steel is close to $


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Da)Zn:?!>B. Euality control of such electrolytes re3uires the regular analysis of Zn, Da?! and

DaD. The ratio of DaD 0 Zn can vary between ) to 5 depending upon the bath temperature and

desired deposit brightness level.The following chart illustrates the typical cyanide electrolyte

options used to plate at room temperature0

Cyanide bath composition

Zinc Sodium hydroxide

Low cyanide +7&* g/1 :*.-7&.5 oz/gal> F74* g/1 :&*7&) oz/gal> &*7

Mid cyanide &7)* g/1 :).*7).F oz/gal> F74* g/1 :&*7&) oz/gal> )7B

igh cyanide )75 g/1 :5.B7B.F oz/gal> F74* g/1 :&*7&) oz/gal> -*7&**

Alkaline non!cyanide electrolytes %edit'

• ontain zinc and sodium hydro@ide. 6ost of them are brightened by proprietary addition agents

similar to those used in cyanide baths. The addition of 3uaternary amine additives contribute to

the improved metal distribution between high and low current density areas. "epending upon the

desired performance, the electroplater can select the highest zinc content for increased

productivity or lower zinc content for a better throwing power :into low current density areas>. Gor

ideal metal distribution, Zn metal evolutes between +7&B g/1 :*.-7&.4 oz/gal> and Da?! at &)* g/1

:&+ oz/gal>. 2ut for the highest productivity, Zn metal is between &B7) g/1 :&.475.B oz/gal>and

Da?! remains at &)* g/1 :&+ oz/gal>.

Acidic electrolytes %edit'

igh speed electrolytes %edit'

• "edicated to plating at high speed in plants where the shortest plating time is critical :i.e. steel

coil or pipe that runs at up to )** m/min :ft/min>. The baths contain zinc sulfate and chloride to

the ma@imum solubility level. 2oric acid may be used as a p! buffer and to reduce the burning

effect at high current densities. These baths contain very few grain refiners. If one is utilized, it

may be sodium saccharine.

"raditional electrolytes %edit'

• Initially based on ammonium chloride, options today include ammonium, potassium or mi@ed

ammonium/potassium electrolytes. The chosen content of zinc depends on the re3uired

productivity and part configuration. !igh zinc improves the baths efficiency :plating speed>, while

lower levels improve the baths ability to throw into low current densities. Typically, the Zn metal

level varies between )* and * g/1 :).F7+.F oz/gal>. The p! varies between B.- and .- units. The

following chart illustrates a typical all potassium chloride bath composition0

http://en.wikipedia.org/w/index.php?title=Hydroxyde&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Electrogalvanization&action=edit&section=5http://en.wikipedia.org/w/index.php?title=Electrogalvanization&action=edit&section=6http://en.wikipedia.org/w/index.php?title=Electrogalvanization&action=edit&section=6http://en.wikipedia.org/w/index.php?title=Electrogalvanization&action=edit&section=7http://en.wikipedia.org/w/index.php?title=Electrogalvanization&action=edit&section=7http://en.wikipedia.org/wiki/Grain_boundary_strengthening#Grain_refinementhttp://en.wikipedia.org/wiki/Grain_boundary_strengthening#Grain_refinementhttp://en.wikipedia.org/w/index.php?title=Electrogalvanization&action=edit&section=8http://en.wikipedia.org/wiki/Ammonium_chloridehttp://en.wikipedia.org/w/index.php?title=Hydroxyde&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Electrogalvanization&action=edit&section=5http://en.wikipedia.org/w/index.php?title=Electrogalvanization&action=edit&section=6http://en.wikipedia.org/w/index.php?title=Electrogalvanization&action=edit&section=7http://en.wikipedia.org/wiki/Grain_boundary_strengthening#Grain_refinementhttp://en.wikipedia.org/w/index.php?title=Electrogalvanization&action=edit&section=8http://en.wikipedia.org/wiki/Ammonium_chloride


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"raditional acid bath composition

#arameters $alue in g%L &oz%gal'

Zinc B* g/l :.B oz/gal>

Total chloride &) g/l :&+.- oz/gal>

Anhydrous zinc chloride -* g/l :&*.F oz/gal>

(otassium chloride &-* g/l :)B.& oz/gal>

2oric acid ) g/l :5.B oz/gal>

•

• Typical grain refiners include low soluble etones and aldehydes. These brightening agents must

be dissolved in alcohol or in hydrotrope. The resultant molecules are co7deposited with the zinc to

produce a slightly leveled, very bright deposit. The bright deposit has also been shown to

decrease chromate/passivate receptivity, however. The result is a reduction in the corrosion

protection afforded.

6alvanizing forms a metallurgical )ond )et$een the zinc and the underlying steel or iron, creating a

)arrier that is part of the metal itself. +uring galvanizing, the molten zinc reacts $ith the surface of the

steel or iron article to form a series of zinciron alloy layers.


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thin at the corners and edges.


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amol-cold galvanizing quations

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