flux and their composition role

1. Hot Dip Galvanizing
The hot dip galvanizing is a process of dipping steel into containing molten zinc to
corrosionprotection. It is required where industries are uses iron and steel. It has the
features of durability, longevity, cost, and sustainability. It protects steel from
corrosionto catholic protection and barrier protection. The hot dip galvanizing is
used in chemical process, pulp and papers, transportation, automotive industries.
Zinc ammonium chloride
Zinc ammonium chloride is the inorganic compound with the formula (NH4)2ZnCl4. It is
the ammonium salt of tetrachlorozincate. It used as a flux in the process of hot-dip galvanizing
Uses
Steel to be galvanized passes through an acidic cleaning process to remove iron oxide "mill
scale".
After this process, the surface of the steel is very active and oxide layers begin forming
immediately upon exposure to the atmosphere.
Zinc ammonium chloride flux in aqueous solution is applied to the steel to reduce any oxides
that are formed and/or inhibit them from forming altogether.
This allows the molten zinc in the proceeding galvanizing step to maximally adhere to and alloy
with the surface of the steel.
Ammonium chloride
Ammonium chloride is an inorganic compound with the formula NH4Cl and a white
crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly
acidic. Sal ammoniac is a name of the natural, mineralogical form of ammonium chloride.
A 5% by weight solution of ammonium chloride in water has a pH in the range 4.6 to 6.0
Applications
Ammonium chloride is used as a flux in preparing metals to be tin coated, galvanized or
soldered.
It works as a flux by cleaning the surface of work pieces by reacting with the metal oxides at the
surface to form a volatile metal chloride.

2. For that purpose, it is sold in blocks at hardware stores for use in cleaning the tip of a soldering
iron, and it can also be included in solder as flux.
zinc chloride and zinc oxide
Aqueous zinc chloride reacts with zinc oxide to form an amorphous cement that
was first investigated in the 1855 by Stanislas Sorel. ...
When hydratedzinc chloride is heated, one obtains a residue of Zn(OH)Cl e.g.
ZnCl2·2H2O → ZnCl(OH) + HCl + H2O. The compound ZnCl.
Zinc chloride
Zinc chloride is the name of chemical compound ZnCl2 or its hydrates. All zinc chlorides are colorless or
white and highly soluble in water. ZnCl2 itself is hygroscopic and can be considered deliquescent.
Samples should therefore be protected from sources of moisture, such as the atmosphere.
Zinc chloride finds wide application in textile processing, metallurgical fluxes and chemical synthesis.
Uses
ZnCl2 is used as a flux for soldering because of its ability (when molten) to dissolve metal oxides.
Typically this flux was prepared by dissolving zinc foil in dilute hydrochloric acid until the liquid ceased to
evolve hydrogen, for this reason such flux was known as killed spirits. because of its corrosive nature it is
not a suitable flux for situations where any residue cannot be cleaned totally away, such as electronic
work.
It is strongly deliquescent (water-absorbing) and is utilized as a drying agent and as
a flux. In aqueous solution it is used as a wood… Zinc sulfate and zinc chloride are
used in a wide range of comparatively small-scale applications.
Zinc oxide
Zinc oxide is an inorganic compound with the formula ZnO. ZnO is a white powder that is
insoluble in water, and it is widely used as an additive in numerous materials and products
including rubbers, plastics, ceramics, glass, cement, lubricants,[5]
paints, ointments, adhesives,
sealants, pigments, foods, batteries, ferrites, fire retardants, and first-aid tapes.
Crystalline zinc oxide is thermochromic, changing from white to yellow when heated in air and
reverting to white on cooling.[9]
This color change is caused by a small loss of oxygen to the

3. environment at high temperatures to form the non-stoichiometric Zn1+xO, where at 800 °C, x =
0.00007
ZnO reacts slowly with fatty acids in oils to produce the corresponding carboxylates, such
as oleate or stearate.
ZnO forms cement-like products when mixed with a strong aqueous solution of zinc chloride and
these are best described as zinc hydroxy chlorides
Applications
Coatings
Paints containing zinc oxide powder have long been utilized as anticorrosive coatings for
metals. They are especially effective for galvanized iron. Iron is difficult to protect because its
reactivity with organic coatings leads to brittleness and lack of adhesion. Zinc oxide paints retain
their flexibility and adherence on such surfaces for many years.[54]
ZnO highly n-type doped with aluminium, gallium, or indium is transparent and conductive
(transparency ~90%, lowest resistivity ~10−4
Ω·cm[85]
). ZnO:Al coatings are used for energy-
saving or heat-protecting windows. The coating lets the visible part of the spectrum in but either
reflects the infrared (IR) radiation back into the room (energy saving) or does not let the IR
radiation into the room (heat protection), depending on which side of the window has the
coating.[8]
Plastics, such as polyethylene naphthalate (PEN), can be protected by applying zinc oxide
coating. The coating reduces the diffusion of oxygen with PEN.[86]
Zinc oxide layers can also be
used on polycarbonate (PC) in outdoor applications. The coating protects PC from solar
radiation and decreases the oxidation rate and photo-yellowing of PC
Safety
As a food additive, zinc oxide is on the U.S. FDA's list of generally recognized as safe, or
GRAS, substances.[107]
Zinc oxide itself is non-toxic; however it is hazardous to inhale zinc oxide fumes, as generated
when zinc or zinc alloys are melted and oxidized at high temperature. This problem occurs while
melting brass because the melting point of brass is close to the boiling point of
zinc.[108] Exposure to zinc oxide in the air, which also occurs while welding galvanized (zinc
plated) steel, can result in a nervous malady called metal fume fever. For this reason, typically
galvanized steel is not welded, or the zinc is removed first
Note:
 when ammonium chloride is dissolved in water, it gives an acidic solution
because ammonium ion is a strong conjugate acid of the weak base

4. ammonia, but chloride ion is a weak conjugate base of the strong acid
hydrochloric acid.
