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7/31/2019 Surface Coating Alloys
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Surface Coating Alloys
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Why surface coating?
Annual loss due to corrosion isestimated to be 3-5 % of GNP, about80,000 Cr `/ year
Direct Loss: material cost, over design,use of costly material
Indirect losses: loss of production,contamination of product, liability inaccidents
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Corrosion inIndia
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Coated Steels
Most common metallic coating forcorrosion protection of steel is a zinc(sacrificial coating)
Offers Barrier and Galvanic protection
Scrat
ch ElectrolyteZincCoatingSteel
Substrate
Zinc
and
Steel
forms of alloy
used Zinc, PureAl,
Al-Zn and
Zn-Al-Si alloy
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Surface Coating Alloy composition usedworldwide
Chemical Composition(%)
Zn Si Fe Al
43 ---- -- 55
12-24 Up to 4 0.25 Balance
12-24 0.3-4 0.3-3.5 Balance
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AlZnSi Alloy (Galvalume)
Minex manufactures Pre-mixed
AlZnSi alloy and
Aluminum Silicon master alloys
AlZnSi Alloy
- assures consistent alloy chemistry
- ease of addition and control
- close control on coating bath
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Minex Manufacturing Facilities
Coating alloysmanufactured at Nimji
2 set of 1MT InductionFurnace
1MT Uni DirectionalStirring Furnace
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Minex Manufacturing Facilities
ISO 9001:2008 andNABL accredited labfacilities
Adherence to strictquality control during
production andprocess
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Minex Manufacturing Facilities
Alloys manufacturedwith ASTM standardsand specifications
500 Kgs to 1MT castsize or Custom sows
for large capacity
Use of AlSi 50% alloy
for close control of
d i
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Raw MaterialAluminum Melt +
AlSi50 & Zinc Metal
Weighing as perrequirement
RM Inspection by Lab
Transfer Aluminum Meltfrom Skelner Furnace to
UDS
(temp. 70015C)
Dissolve AlSi50 alloy inAluminum Melt
After dissolution clean dross(temp. 76015C)
Zn Metal added in AlSi meltTill homogenization
Cleaning of C.I.mould, maintain
mould temp in range150C max, with
mould wash coating
Sample token is withdrawnfor Chemical Analysis
Dilution or addition ofmaterial depends upon
sample analysis
Alloy Casting in C I mould(temp. 68515C)
Results Analyzedwith ED-XRF
Ingot Surface FinishAnalyzed for packing &
dispatch
Mould:Mass ratio >1.5is for better heat
dissipation
ProductionProcessRM used
EC grade Al
AlSi 50
Zn metal???
Element Al Si Fe Others
% 99.70 0.10Max
0.20Max
traces
Element Al Si Fe Ca
% 50.0 50.0
Max
0.20
Max
0.10
Max
Element Zn Si Fe others
% 99.0 0.20
Max
0.20
Max
0.10
Max
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Minex Alloyfor Surface Coating
AlloyGrade
Chemical Composition (%)Al Zn Si Fe
(max)Cu(max)
Cd(max)
Pub(max)
Sn(max)
Ni(max)
Ti+Ba+Cr(max)
Al-Zn-Si
Alloy
55 -
58
41-
43
1.5-2 0.25 0.03 0.05 0.01 0.05 0.05 0.05
Alloy
Composition
Ingot Forms
AlSi 3% Finished AlloyElement Si Fe Others Al% 2.8-3.2 0.20 max Trace Balance
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Advantage
AlZnSi coating alloy v/s AlSi master alloy
Coating alloy directly melted in coating
tank Consistent alloy chemistry restricts
charge balance for each alloy addition
Alloy chemistry designed with closetolerance over tramp and impurities
High degree of homogeneity with UDSfurnace
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Advantage and Effects
Corrosion performance is mostly relatedto Al Zn alloy,
Silicon addition minimize the growth of
brittle intermetallic layer of steel andzinc
during Hot Dip Process.
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Al-Zn-Si alloy microstructure2 layers i.e.an Al Zn overlay coating and Fe
containing intermetallic/alloy layer.
Alloy layer forms at the interface between thecoating and steel substrate.
Due to this, Al Zn Si Alloy combines the Galvanic corrosion protection of Zn with the barrier protectionof Aluminum
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thank
you!