Chapter one
Introduction
1.1 Background of Study
Students’ Industrial Work-experience Scheme (SIWES) is one of the Industrial
Training Fund (ITF) programme which was introduced in 1974 due to the inability
of engineering and technology students in Nigeria universities and polytechnics to
meet the practical aspects of their training. That is, the needs to enable students
match their theoretical school knowledge with the practical aspect of their training
in industry. The Training lasts for six months. According to Ekpenyong (2011),
one of the principles underlying any industrial work experience scheme for
students in institutions of learning is the desire to marry the practical with the
theoretical learning which characterizes conventional classroom situations with a
view to striking a balance between theory and practice. The author stressed further
that it was in realization of this that the ITF when it was established, set out to
study the extent to which the theoretical knowledge that students in engineering
technology and other allied fields in Nigerian institutions offering technology
based courses related to the kind of work experience expected of them by
employers.
The result of the ITF survey showed a great disparity between students’ knowledge
and their ability to apply it in relevant jobs. In order to bridge the gap between the
1
two, the ITF in 1974 established a co-operative internship programme, which
enabled students of technology to spend some part of their courses for relevant on
the-job practical experiences in appropriate areas of the Nigerian industry
(Ekpenyong, 2011). The author further stressed that the internship programme,
SIWES, can therefore be seen as that which is intended to give Nigerian students
studying occupationally related courses experience that would supplement their
theoretical learning as a well of equipping the students with the needed skills to
function in the world of work.
This need to combine theoretical knowledge with practical skills in order to
produce results in the form of goods and services or to be productive is the essence
and rationale for industrial training, and a basic requirement for the award of
B.Eng.
1.2 Brief history of SIWES
In recognition of the shortcomings and weakness in the formation of SET
graduates, particularly with respect to acquisition of relevant production skills
(RPSs), the Industrial Training Fund (which was itself established in 1971 by
decree 47) initiated the Students’ Industrial Work-experience Scheme (SIWES) in
1973. The scheme was designed to expose students to the industrial environment
and enable them develop occupational competencies so that they can readily
2
contribute their quota to national economic and technological development after
graduation.
Consequently, SIWES is a planned and structured programme based on stated and
specific career objectives which are geared toward developing the occupational
competencies of participants.
In spite of the challenges faced by SIWES in the four decades of its existence, the
Scheme has not only raised consciousness and increased awareness about the need
for training of SET students, but has also helped in the formation of skilled and
competent indigenous manpower which has been manning and managing the
technological resources and industrial sectors of the economy. Participation in
SIWES has become a necessary condition for the award of degrees and diplomas to
SET students graduating from higher institutions in Nigeria. It is therefore, not in
doubt that SIWES is a veritable means or tool for National Economic
Development.
The main thrust of ITF programmes and services is to stimulate human
performance, improve productivity, and induce value-added production in industry
and commerce. Through its SIWES and Vocational and Apprentice Training
Programmes, the Fund also builds capacity for graduates and youth selfemployment, in the context of Small Scale Industrialization, in the economy.
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The Industrial Training Fund is a grade ‘A’ parasternal operating under the aegis of
the Federal Ministry of Industry, Trade and Investment. It has been operating for
42 years as a specialist agency that promotes and encourages the acquisition of
industrial and commercial skills required for national economic development.
1.2.1 Vision Statement
To be the prime Skills Training Development Organization in Nigeria and one of
the best in the world
1.2.2 Mission Statement
To set and regulate standards and offer direct training intervention in industrial and
commercial skills training and development, using a corps of highly competent
professional staff, modern techniques and technology.
1.3 Aim of SIWES
The effort is aimed at helping/training students in the Nigerian tertiary institutions
the practical aspect of their field of study by exposing students to machines and
equipment, professional work methods and ways of safeguarding the work areas
and workers in industries and other organizations.
1.4 Objectives of SIWES
The Industrial Training Fund’s policy Document No. 1 of 1973 which established
SIWES outlined the objectives of the scheme. The objectives are to:
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1) It provides an avenue for students in institutions of higher learning to acquire
industrial skills and experience during their course of study.
2) It exposes Students to work methods and techniques in handling equipment and
machinery that may not be available in their institutions.
3) It makes the transition from school to the world of work easier and enhances
students’ contact for later job placements and a chance to evaluate companies for
which they might wish to work.
4) It provides students with the opportunities to apply their educational knowledge
in real work and industrial situations, there by bridging the gap between theory and
practice.
5) The programme teaches the students on how to interact effectively with other
workers and supervisors under various conditions in the organization.
1.5 Importance of SIWES to Agricultural and bioresource engineering
1. It exposes students to more practical work methods and techniques in
Agricultural and bioresource engineering.
2. It provides students in Agricultural and bioresource engineering with an
opportunity to apply their theoretical knowledge to real life situations.
3. It enables students in Agricultural and bioresource engineering to gain
experience in handling equipment and machineries.
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4. It provides an environment whereby students in Agricultural and bioresource
engineering can develop their creativity and interpersonal skills through software
design techniques.
5. It is one of the requirements for the award of Bachelors of Engineering (B.Engr.)
in Agricultural and bioresource engineering.
1.6 Justification for choice of industry
Theoretical knowledge alone would not usually prepare and prepare an educated
person for the world of work. The worker or productive individual must not only
be knowledgeable but also be versatile in the application of skills to perform
defined jobs or work.
Both education and training are important; there cannot be effective education
without some training input and there cannot be effective training without some
educational input. The productive individual, particularly in this millennium, must
be able to combine and utilise the outcomes from the two forms of learning
(Know-How Ability and Do-How Capability) for production of goods and services
which is crucial in pursuing careers in science, engineering and technology (SET)
disciplines.
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Chapter two
2.1 About the Company
The first Donmex tech Company was established in 2005 in Kinshasa, the
Democratic Republic of the Congo trading in general merchandise, electronics and
textiles. Three years later Donmex Tech Nigeria commenced business in Lagos,
Nigeria on October 1, 2008. That same year the company also started doing
business in Brazil.
As more family members and other professionals joined the business, their varying
skills and personalities complimented each other and they formed a dream team.
The brothers then opened financing offices in London, Hong Kong and Miami to
compliment the manufacturing operations in Nigeria, India and Brazil and thus
began the rise of Donmex Tech Nigeria into a diversified group with companies
spanning different industries around the globe. The rest, as they say, is history.
2.2 Vision
To improve 100 million lives by 2020.
2.3 Mission
To offer essential products and services that betters the lives of people
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2.4 Donmex Tech Nigeria organogram
Board of directors
Operations manager
secretary
HSE
Coordinating manager
Fin Admin Manager Workshop Manager Chief Engineer
Chief
Account
Purchase
Manager
Account
Dept
Store
Engineers
Trainee and IT
students
Personal Assistant
Others
Drivers
Chief
Security
Admin
Dept
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Chapter three
During my period of Industrial Training in Donmex Tech Nigeria I was based
mainly in the following departments.
 Health , safety and environment department
 Workshop and Galvanizing department
3.1 Health safety and environment
Under this department I went through various courses like
 Personal Protective Equipment training
 Good House Keeping training
 Journey management training
 HSE 1&2 AND HSE 3 Professional training
3.2 Galvanizing
Once the steel is ready for galvanizing, it is immersed in molten zinc. The
chemistry of the bath must meet certain standards, requiring at least 98% pure zinc
and a temperature of 815-850 F. During the bath, the zinc reacts and bonds with
iron in the steel to form an extremely hard alloy layer that strengthens and protects
the steel. Excess zinc is removed from the galvanized piece by draining, vibrating
and/or centrifuge but the metallic reaction continues as long as the steel remains
near bath temperature. Galvanized pieces are cooled by immersing them in a
passive solution, in water, or by being left in open air.
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Fig 1: Simple 3-step Galvanizing Process Protects Steel for a Lifetime
Galvanized steel is prized all over the world for its durability and corrosionresistance. But for as strong as the finished material is, the process is surprisingly
simple and straightforward. Galvanizing steel consists of just three steps:
1. Surface Preparation.
2. Galvanizing.
3. Inspection.
3.3 Surface Preparation
Like most things, the quality of a finished galvanized product is directly influenced
by the amount of effort put into the preparation. Poor surface prep can cause the
galvanization to fail, but galvanization has built-in quality control of sorts. The
zinc used in galvanizing won’t react with an unclean steel surface. This makes it
easy to see poorly coated areas as soon as the piece is pulled out of the
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galvanization tank. Unclean areas remain uncoated, allowing technicians to correct
the problem right away.
Surface preparation consists of three steps:
1. Degreasing/Caustic
Cleaning. An
acidic
“bath”
removes
organic
contaminants from the steel surface. Dirt, paint, grease, and oil can be
removed this way. Materials that cannot be removed via the bath include:
epoxies, vinyls, asphalt, and slag. These contaminants are removed by
degreasing, grit-blasting, sand-blasting, or other mechanical means.
2. Picking. A dilute solution of acid is used to remove mill scale and rust from
the steel. Instead of or in place of the acid, an abrasive cleaner or air blasted
sand could be used.
3. Fluxing. Fluxing is a zinc ammonium chloride solution that removes
remaining rust particles and adds a protective layer to the steel, helping to
prevent any further oxides from forming on the surface before it can be
galvanized.
3.4 Galvanizing Process
Hot-dip galvanizing is the process of immersing iron or steel in a bath of molten
zinc to produce a corrosion resistant, multi-layered coating of zinc-iron alloy and
zinc metal. While the steel is immersed in the zinc, a metallurgical reaction occurs
between the iron in the steel and the molten zinc. This reaction is a diffusion
11
process, so the coating forms perpendicular to all surfaces creating a uniform
thickness throughout the part.
Fig 2: Galvanizing Process
The hot-dip galvanizing process has been used since 1742, providing long-lasting,
maintenance-free corrosion protection at a reasonable cost for decades. Although
hot-dip galvanizing has been utilized to protect steel for generations, the
galvanizing process continues to evolve with new technologies and creative
chemistries. The three main steps in the hot-dip galvanizing process are surface
preparation, galvanizing, and post-treatment, each of which will be discussed in
detail. The process is inherently simple, which is a distinct advantage over other
corrosion protection methods.
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This shows a series of steel structures with visible evidence of corrosion. Rust and
corrosion are expensive for owners and taxpayers. Deteriorating buildings, roads,
bridges, etc. are costly to repair, and without sufficient corrosion protection,
maintenance is done often, or in the worst cases, the structure must be rebuilt. With
the push toward sustainable development, specifying structures with longevity that
require little maintenance over time provide both environmental and economic
benefits.
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14
3.5 Inspection
The last step, the inspection process, is also the quickest. Coating thickness and
surface condition are both closely scrutinized for integrity. Several tests are used to
determine coating thickness, uniformity, adherence, and appearance. Results are
compared to long-established and accepted standards set by the ASTM, the
International Standards Organization (ISO), the Canadian Standards Association
(CSA), and the American Association of State Highway and Transportation
Officials (AASHTO).
3.5.1 Types of Inspection
a. Adherence Test
Testing zinc coating adherence is achieved using a stout knife and smoothly
running it along the surface of the steel without whittling and gouging, as detailed
in the ASTM specifications A123/A123M and A153/A153M. The knife should put
a slight mark in the zinc metal surface, but should not cause any flaking or
delamination of the layers. Paring or whittling with the knife is not acceptable, and
the test should not be performed on corners or edges of the product. Because
flaking or peeling of the zinc coating is usually quite obvious and uncommon, the
stout knife test, which is a referee test, is rarely performed.
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b. Embrittlement Test
When there is suspicion of potential embrittlement of a product, it may be
necessary to test a small group of the products to measure the ductility according to
the protocol in the specification ASTM A143/A143M. These tests are usually
destructive to the zinc coating and possibly to the product as well. Depending on
the service conditions the product will be exposed to, one of three embrittlement
tests - similar bend radius test, sharp blow test, and steel angle test - may need to
be performed. The embrittlement test uses a known force to provide a stress that
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should be lower than the yield stress of the part. If there is a fracture or permanent
damage created during the testing process, the parts must be rejected.
c. Passivation Testing
The specification to determine the presence of chromate on zinc surfaces is ASTM
B201. This test involves placing drops of a lead acetate solution on the surface of
the product, waiting 5 seconds, and then blotting it gently. If this solution creates a
dark deposit or black stain, there is unpassivated zinc present. A clear result
indicates the presence of a passivation coating.
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3.6 Hot-dip galvanization
Hot-dip galvanization is a form of galvanization. It is the process of coating iron
and steel with zinc, which alloys with the surface of the base metal when
immersing the metal in a bath of molten zinc at a temperature of around 450 °C
(842 °F). When exposed to the atmosphere, the pure zinc (Zn) reacts with oxygen
(O2) to form zinc oxide (ZnO), which further reacts with carbon dioxide (CO2) to
form zinc carbonate (ZnCO3), a usually dull grey, fairly strong material that
protects the steel underneath from further corrosion in many circumstances.
Galvanized steel is widely used in applications where corrosion resistance is
needed without the cost of stainless steel, and is considered superior in terms of
cost and life-cycle. It can be identified by the crystallization patterning on the
surface (often called a "spangle").
Fig 3: Hot-dip galvanizing consists of a sequence of steps
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Galvanized steel can be welded; however, one must exercise caution around the
resulting toxic zinc fumes. Galvanized fumes are released when the galvanized
metal reaches a certain temperature. This temperature varies by the galvanization
process used. In long-term, continuous exposure, the recommended maximum
temperature for hot-dip galvanized steel is 200 °C (392 °F), according to the
American Galvanizers Association. The use of galvanized steel at temperatures
above this will result in peeling of the zinc at the inter metallic layer[citation needed].
Electrogalvanized sheet steel is often used in automotive manufacturing to enhance
the corrosion performance of exterior body panels; this is, however, a completely
different process which tends to achieve lower coating thicknesses of zinc.
Like other corrosion protection systems, galvanizing protects steel by acting as a
barrier between steel and the atmosphere. However, zinc is a more electropositive
(active) metal in comparison to steel. This is a unique characteristic for
galvanizing, which means that when a galvanized coating is damaged and steel is
exposed to the atmosphere, zinc can continue to protect steel through galvanic
corrosion (often within an annulus of 5 mm, above which electron transfer rate
decreases).
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3.7 Cold Galvanizing
Cold galvanizing is simply the application of a zinc-rich paint to the surface of a
steel element to protect it from corrosion. As such, the term “cold galvanizing” is
considered to be a misnomer among some professionals in the coating industry.
Zinc paints may be applied by brushes, rollers, spray guns, etc. Coatings may also
be applied by the electrogalvanizing method as well. The zinc-rich paints used in
cold galvanizing are different from conventional coatings due to the presence of a
binding compound. These binders allow the zinc to mechanically bond to the steel
to offer an effective level of protection.
Like hot-dip galvanizing, cold galvanizing can provide barrier protection and also
some degree of cathodic protection. However, the zinc dust present in the paint or
coating must be in high enough concentrations to promote electrical conductivity
between the steel and the zinc. The surface preparation required for applying zincrich coatings is less demanding than hot-dip techniques. Before coatings operations
begin, the surface of the steel must be clean and dry. Usually, a wire brush is first
used to remove rust or any other corrosion products that may be present. Dirt,
grease, chemicals and other organic compounds must also be removed accordingly.
Once the surface is prepared, the zinc coating is applied to the surface in as many
coats as required.
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3.8 Comparing Hot-dip and Cold Galvanizing
Although hot-dip and cold galvanizing both serve similar purposes, their method of
application and performance differ significantly. Cold galvanizing, unfortunately,
does not offer the same level of protection as its hot-dip counterpart. Because cold
galvanizing is simply a coating, it cannot bond with the metal on a chemical level
and, as such, does not have the same durability, abrasion resistance and cathodic
protection capabilities as hot-dip galvanizing.
While cold galvanizing does not live up to the performance of hot-dip galvanizing,
it does have its benefits. Cold galvanizing is ideal for cost-effective and rapid
application on smaller structures and components. Hot-dip processes are more
expensive and better suited for larger structures, typically for heavy-duty industrial
uses. The choice of galvanizing method ultimately boils down to finding the right
balance between cost and coating performance for a given application.
3.9 Surface Preparation Prior to Hot-Dip Galvanizing
Batch hot-dip galvanizers have a simple process they use to prepare steel or iron
prior to galvanizing. After the steel has been inspected to ensure it has adequate
vent and drain holes, it is dipped into a series of cleaning chemicals. The first
chemical is a degreasing bath that removes organic contaminants such as dirt,
grease, and oil from the metal. The next chemical used is pickling acid, which
removes mill scale and rust (oxides) from the steel. The last step before
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galvanizing is dipping the steel or iron into a flux bath, which prevents oxidation of
the metal prior to entering the galvanizing bath and also aids the galvanizing
reaction in developing the hot-dip galvanized coating.
Fig 4: Schematic diagram of a typical batch hot-dip galvanizing line
ASTM specifications do not have required parameters for cleaning chemicals used
in the galvanizing process. There are general concentration ranges these chemicals
are most effective and each galvanizer optimizes their cleaning chemicals to give
them the best results at cleaning the steel or iron and achieving a high-quality hotdip galvanized coating.
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Fig 5: Hot-Dip Galvanizing flowchart
3.10 Principle of hot dip galvanization
The principle of hot dip galvanizing is simply that the cleaned iron parts are soaked
in zinc bath through the wetting action of the coplating agent to make the steel
react with the molten zinc to form a alloyed leather film. Good hot dip galvanizing
operations should be under strict control of all processes, fully play the function of
the process. And if the operation of the previous process is not good enough, it will
cause a chain of adverse reactions to the subsequent process, and a large increase
in the cost of operation or cause bad hot dip galvanizing products. If the
pretreatment is not good, the molten zinc can not fully react with the steel to form
the most perfect galvanized film. If the post-treatment is not good, it will damage
the appearance of the galvanized film and reduce the value of the goods.
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3.11 Advantages
1. The entire steel surface is protected, and it is easy for the dissolved zinc to be
covered uniformly, no matter in the inner part of the pipe in the depression or any
other corner where the coating is difficult to enter.
2. The hardness of galvanizing layer is greater than that of steel. The top-layer Eta
layer has only 70 DPN hardness, so it is easy to be dented by collision. However,
the lower Zeta layer and delta layer have 179 DPN hardness values and 211 DPN
hardness values, respectively, which are higher than the 159 DPN hardness values
of iron, so its impact resistance and abrasion resistance are quite good.
3. In the corner area, the zinc layer is often thicker than other areas, and has good
toughness and abrasion resistance. And other coating is in this corner place, often
be the thinnest the least easy to construct, the most vulnerable injury, therefore
often must maintain again.
4. Even if it is due to heavy mechanical injury or other reasons. When a small part
of the zinc layer falls off and the iron base is exposed, the surrounding zinc layer
ACTS as a sacrificial anode to protect the steel here from erosion. Other coatings,
on the other hand, are just the opposite, rust will be generated immediately and
quickly spread below the coating, causing the coating to peel off.
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5. The depletion of zinc layer in the atmosphere is very slow, about 1/17 to 1/18 of
the corrosion rate of steel, and can be estimated. Its life is much longer than any
other coating.
6. Coating life in a specific environment depends mainly on the thickness of the
coating. The thickness of the plating layer is determined by the thickness of the
steel, that is, the thicker the steel is easier to get the thicker the plating layer, so the
thicker steel part in the same steel structure must also get the thicker the plating
layer, so as to guarantee the longer life.
7. Due to aesthetics, art, or the use of a certain serious corrosive environment, the
galvanized coating can be applied to deal with the duplex system again. As long as
the paint system is correctly selected and easy to be constructed, the anticorrosion
effect is 1.5~2.5 times better than that of the single painting and hot dip zinc
combined.
8. To protect steel with zinc coating, there are several other methods besides hot
dip galvanizing. Generally, hot dip galvanizing method is the most widely used,
has the best corrosion protection effect and has the best economic benefits.
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3.12 Materials the Cleaning Chemicals Cannot Remove
There are some materials the cleaning chemicals used prior to galvanizing cannot
remove or have great difficulty removing. Here is a list of the most common of
these materials:

Weld slag and other welding flux residues

Weld splatter and anti-splatter

Burrs (could include excessively rough edges from flame cutting)

Very heavy or extremely adherent mill scale

Mill coatings such as varnishes or lacquers present on some types of pipe

Epoxies, types of vinyl, and asphalt
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
Sand and other impurities on castings

Oil-based paints and markers

Crayon markers

Very heavy or thick deposits of wax or grease
These materials should be removed from the metal prior to it being delivered to the
galvanizing plant. SSPC and NACE have a variety of commonly used standards for
abrasive blast cleaning, hand cleaning, and power tool cleaning, effective at
removing these materials. Abrasive blasting is usually necessary on castings to
remove sand and other impurities from the casting process. Alternatively, different
products can be used on the steel or iron which are compatible with the hot-dip
galvanizing process to reduce the need for blasting or hand/power tool cleaning.
For example, using uncoated electrodes avoids the problem of depositing flux on
the metal during welding, and galvanizing-safe markers are available that dissolve
in the cleaning baths used in the galvanizing process. Different types
(specifications) of pipe can be ordered that are free of mill coatings such as
varnishes, lacquers, or oils.
3.13 Other Considerations
Some specifiers use generic preparation processes for steel or iron that will be
coated, such as always abrasive blasting it. In most cases, this is not necessary
prior to the galvanizing process unless the metal to be galvanized is contaminated
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with the materials listed above. The cleaning steps prior to the hot-dipping process
adequately clean the metal and ensure a high-quality hot-dip galvanized coating
develops on the metal. In fact, the only way a galvanized coating can develop is if
the metal is free of organic contaminants, mill scale, and oxides. This is a built-in
quality control process in that if a galvanized coating has developed, the
underlying metal must have been free of contaminants.
3.14 Kind of Contaminants Need to Be Removed for Steel Surface Treatment
Rust – All steel is susceptible to corrosion if it is not treated beforehand. There are
many different types, ranging from uniform attack corrosion, to pitting corrosion.
The type of corrosion will dictate what rust grade the steel is. Some grades should
be avoided, such as pitted steel, which can be very difficult to clean.
Mill Sale – Mill scale is the flaky surface of hot rolled steel, consisting of different
iron oxides. It is a nuisance when the steel needs to be processed. Any paint
applied over it is wasted, since it will come off with the scale as moisture-laden air
gets under it. Hence it needs to be removed.
Grease, Oil, Dirt and Dust – When preparing steel, anything that might prevent
the paint wetting out or adhering to the surface needs to be removed. This includes
grease and oils, as well as dirt, dust and salts.
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3.15 Common Methods of Steel Preparation
Solvent Cleaning – Before any further cleaning or preparation, steel sections are
first wiped down with acetone, a thinner, or another type of solvent. This helps
remove mill scale, oxides, and some corrosion.
Abrasive Grit Blasting – Grit blasting is the most effective method for removal of
particularly difficult dirt, mill scale, rust and old coatings and other impurities.
This is achieved using a shot-blasting machine, which the raw steel is passed
through.
Prior to blasting, steelwork needs to be cleaned of any oils or grease. It is then
blasted with shot or another abrasive material, which bombardes the steel surface,
removing any impurities. The machine then brushes off any debris. There are all
different types of classifications for blast cleaning a steel section, which will
depend on what it is being used for, and what is being done afterwards (such as
painting, coating or welding).
Hand & Power Tool Cleaning – Scrapers, wire brushes and other hand held tools
are relatively ineffective in removing mill scale or corrosion. However, power
tools like rotary brushes, rotary grinders, and needle guns may be useful for
cleaning hard-to-reach places where grit blasting is not possible.
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Acid Pickling – This involves immersing the steel in a bath of suitable inhibited
acids that dissolve or remove the mill scale and rust. This technique is normally
only used for structural steel intended for hot-dip galvanising.
Flame Cleaning – This involves passing an oxy/gas flame over the steel surface.
The heat causes rust scales to flake off, which can then be removed by scraping
and wire brushing followed by dust removal. It is not he most efficient process and
is rarely used.
Wet Abrasive Blast Cleaning – As the name implies, this is similar to the girt
blasting technique, however, water is employed rather than shot. This contributes
to the reduction of a dust hazard, particularly when removing lead-based paints and
water-soluble contaminants. Ultra-high pressure water jetting is also used, which is
favoured by some because it removes high percentages of soluble salts from the
surface.
3.16 Flux Cleaning Method for Continuous Galvanizing
There is one other method for providing a clean oxide-free steel surface to a
galvanizing bath, viz., the use of chemical fluxes. It is an older, and now a far less
common method than the process described above, but is a proven means of
obtaining very good coating adhesion. The flux galvanizing process is also used in
the after-fabrication, batch galvanizing industry for articles such as structural
shapes, pipe, etc.
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The normal procedure for continuous flux galvanizing of steel sheet involves a
cleaning/degreasing step, often using a similar aqueous alkaline cleaning solution
to that used for the hydrogen cleaning process. Following this is an acid-pickling
step (usually hydrochloric acid) to remove surface oxides. After pickling and
during the time that the sheet is rinsed and dried, a very thin oxide layer reforms on
the steel surface. The reason this happens is that oxide-free low carbon steel reacts
very quickly in air to form a thin surface oxide layer. It is essentially impossible to
prevent this reaction. This oxide layer does not perceptibly change the appearance
of the steel surface, although the surface may be slightly darker than an absolutely
oxide-free surface. The color is not the usual black or red iron oxide normally
associated with rusting, but a thin oxide is present. This thin film must be removed
in order to get rapid, complete wetting of the steel by the molten zinc. Therefore,
one more step is needed ahead of the coating bath.
Since flux coating lines do not have an annealing furnace as part of the process (the
sheet’s mechanical properties are obtained in annealing and skin passing
operations ahead of the galvanizing line), hydrogen cleaning is not possible.
Instead, chemicals are used to dissolve the last vestiges of oxide. These chemicals
are called fluxes, much like the fluxes used for processes such as soldering. They
are
simply
compounds
capable
of
dissolving
the
oxides
of
iron.
For galvanizing, the most common flux used, and one that has been around for
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many years, is based on the inorganic chemical “zinc ammonium chloride”. The
weight ratios of zinc chloride to ammonium chloride can be adjusted to meet
individual customer needs. Typically, these solutions also contain special
proprietary wetting agents, anti-foaming agents, and possibly other viscosityadjusting additions. Zinc ammonium chloride fluxes are used for all types of
galvanizing - after-fabrication galvanizing as well as continuous sheet, wire, and
tube galvanizing operations.
As flux is a relatively low melting temperature inorganic chemical, the steel sheet
cannot be heated to high temperatures ahead of the galvanizing bath. If the steel
temperature becomes too hot, the chemical flux will be burned, detracting from its
performance. This means the sheet must enter the galvanizing bath at a temperature
considerably below the zinc metal temperature (860-875°F [460-470°C]). The zinc
pot therefore has to have a much higher heating capability than a typical coating
pot used on lines that have in-line annealing. This high heating capability,
combined with the need to remove the “spent” flux from the surface, usually leads
to a less efficient use of the zinc metal than for coating lines that utilize in-line
annealing and hydrogen cleaning. Flux fumes are also generated and must be
collected by hoods located above the zinc pot. Another feature of flux
coating lines is that the coated product has natural small, flat spangle – even with
lead-bearing zinc. This is a result of the fast, post-pot cooling resulting from the
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sheet’s low pot entry temperature. In the continuous sheet galvanizing process, the
flux can be applied as a “preflux”, that is, applied from a water- based solution that
contains the dissolved flux chemicals, or it can be applied as a “top flux”, that is, a
molten flux layer floating on top of the galvanizing bath. In some cases, both types
of flux application are used.
Continuous galvanizing using fluxes has been a commercial process for many
years. In fact, before the development of continuous galvanizing, the zinc coating
of steel sheet was done by operators immersing sheets, one at a time, into a bath of
molten zinc. Zinc ammonium chloride fluxing was part of that operation. The
movement to continuous galvanizing, using fluxes as a part of the process, was a
natural outgrowth of the one-sheet-at-a- time process. Flux galvanizing lines were
also known as “Cold Galvanizing Lines”, or “Wheeling Lines” (the first steel
company to use them), or “Cook-Norteman Lines” (the process developers) The
downside of flux lines in the case of flat products, however, is that the steel must
be annealed and temper rolled prior to galvanizing.
3.17 Galvanizing Standards
There are certain specifications that have been developed for hot-dip galvanizing in
order to produce a high-quality coating. There are three main standards that govern
the hot-dip galvanized steel, and a handful of supporting specifications that design
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engineers and fabricators should become familiar with to promote a high-quality
coating and ensure their steel design is suitable for hot-dip galvanizing.
3.18 ASTM Standards
The three governing ASTM specifications for hot-dip galvanizing are:

ASTM
A123/A123M:
Standard
Specification
for
Zinc
(Hot-Dip
Galvanized) Coatings on Iron and Steel Products
o
Single pieces of steel or fabrications with different types of steel
products

ASTM A153/A153M: Standard Specification for Zinc Coating (Hot-Dip)
on Iron and Hardware
o
Fasteners and small products that are centrifuged after galvanizing to
remove excess zinc

ASTM A767/A767M: Standard Specification for Zinc-Coated (Galvanized)
Steel Bars for Concrete Reinforcement
o
Reinforcing steel or rebar
3.19 Other Galvanizing Standards
There are also a few international governing standards to be aware of:

CSA G164: Hot-Dip Galvanizing of Irregularly Shaped Article (Note: The
scope of this standard was revised in 2018 to include products intended or
primarily for use in electrical and communication systems only.)
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
ISO 1461: Hot-Dip Galvanized Coatings on Fabricated Iron and Steel
Assemblies Specifications and Test Mehtods

AASHTO M111 (ASTM A123): Zinc (Hot-Dip Galvanized) Coatings on
Iron and Steel Products

AASHTO M232 (ASTM A153): Zinc Coating (Hot-Dip) on Iron and Steel
Hardware
In addition to the governing standards, there are a handful of pre- and postgalvanizing supporting specifications that a specifier/designer should also be
familiar with:
3.20 Pre-Galvanizing

ASTM
A143/A143M: Standard
Practice
for
Safeguarding
Against
Embrittlement of Hot-Dip Galvanized Structural Steel Products and
Procedure for Detecting Embrittlement

ASTM A384/A384M: Standard Practice for Safeguarding Against Warpage
and Distortion During Hot-Dip Galvanizing of Steel Assemblies

ASTM A385/A385M: Standard Practice for Providing High-Quality Zinc
Coatings (Hot-Dip)

ASTM B6: Standard Specification for Zinc
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3.21 Post-Galvanizing

ASTM A780: Practice for Repair of Damaged and Uncoated Areas of HotDip Galvanized Coatings

ASTM D6386: Practice for Preparation of Zinc (Hot-Dip Galvanized)
Coated Iron and Steel Product and Hardware Surfaces for Paint

ASTM D7803: Practice for Preparation of Zinc (Hot-Dip Galvanized)
Coated Iron and Steel Product and Hardware Surfaces for Powder Coating

ASTM E376: Standard Practice for Measuring Coating Thickness by
Magnetic-Field or Eddy-Current (Electromagnetic) Examination Methods
36
Chapter four
4.1 Problems encountered
During the period of attachment, some problems were encountered most of which
were:
4.1.1 Transportation
The problem of transportation was one of the major challenges I had during the
training period. The location of the company was far from my place of residence .
So I had to take the trouble of waking up very early in the morning in order to beat
the early morning hold up so as to get to work on time. Not to talk of the
inconvenience faced in boarding a commercial vehicle to work. Most at times
before one gets to work, you would either be sweating furiously or your ironed
clothes would become rumpled due to how passengers are squeezed in the
commercial vehicles.
Also, the transport fare from my residence to and fro was very expensive. And my
allowance did not help matters because it was quite low compare to how much I
was spending on transport for the month. So I was most of the time relying on my
parents on transport issues.
4.1.2 Finance
The problem of finance was encountered due to the little financial
support from my place of IT. Though I was placed on monthly allowance but it
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was next to nothing. My allowance was quite low . It was just rather too small to
be used to do any tangible thing. This made me almost always on a tight budget
4.1.3 Feeding
The problem of feeding was based on a daily bases. The company doesn’t provide
feeding so I either have to carry food all the way from home going through public
transport struggle with it or during break I would step out and buy food from an
eatery/fast food. On my own part, I barely had transport fare not to talk of feeding
money. This made me not to go out often for breaks on most occasions during my
period of attachment. Due to lack of feeding from my company and lack of money
from myself, I was forced to convert my launch time to siesta time. Thou on some
occasions I had to go out for launch sponsored by my co-workers.
4.2 Recommendations
The following recommendations are made:
 ITF should pay students during the training to alleviate the problems of
feeding, accommodation and transportation rather than wait till the end of
the program.
 The present allowance should be reviewed upward to reflect the present
economic realities.
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 ITF should as a matter of policy, ensure that employers of labour and
establishments where students are doing their Industrial Training; provide
decent accommodation for the students that far from the work place.
 ITF should increase college-based supervisors’ allowance, to ensure that
they effectively supervise their students since many do not visit their
students throughout the period of attachment, their reason being that they do
not get enough allowance from ITF for such visits.
 Federal Government should mandate employers to pay stipulated amounts to
students on industrial training to aid them meet up with transportation,
feeding and other financial needs.
 Students should be more participative in the program to aid them in their
abilities to be self-employed after graduation.
4.3 Conclusion
The six (6) months Students Industrial Work Experience Scheme (S.I.W.E.S)
which is undergone by tertiary institutional students aids in exposure of students to
the real and practical part of their course of study. The SIWES program make
students appreciate what they have learnt in school, as they try to compare and
apply them to the practical aspect they face in their place of industrial attachment.
The ability for a student to put to practice what has been learnt theoretically;
enhances understanding in his/her program of study.
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The experience and exposure I gained during the training period has made me
come to know more about the practical aspect of my program of study. It is
therefore, my candid opinion that the program be sustained and made better by
some of the recommendations stated in this report so as to aid in the uplifting of
the SIWES program. The program is really an eye-opener to the practical
applications of different program of studies and can aid students to be self
employed after their graduation from the higher institution.
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