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MINISTRY
OF EDUCATION AND TRAINING
VIET NAM ACADEMY
OF SCIENCE AND TECHNOLOGY
GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY
----------------------------
TRUONG THI NAM
Thesis title: STUDYING THE EFFECTS OF SOME ADDITIVES ON THE
ZINC PLATING PROCESS, ORIENTED APPLICATION FOR ALKALINE
NON-CYANIDE ZINC PLATING BATH
SUMMARY OF PHD DISSERTATION
Major: Theoretical Chemistry and Physical Chemistry
Code: 9.44.01.19
HA NOI 2021
This dissertation has been carried out at Graduate university of Science and
Technology, hanoi. Viet Nam Academy of Science and Technology
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Supervisors: Dr. Le Ba Thang
Assoc. Prof. Dr. Nguyen Thi Cam Ha
The thesis will be defended at the Board of Examiners of Graduate university of
Science and Technology, hanoi. Viet Nam Academy of Science and Technology at
…………………….. on ………………..
1. Significance of the study
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The problem of corrosion resistance for metal materials has become an urgent
need for all countries in the world, especially for Vietnam which is located in the
tropical monsoon climate: temperature, High air humidity [1].
Metal coating is one of the methods of corrosion protection that has been
researched and used quite popularly in the world and in Vietnam. Among them, zinc
is one of the most used metal coatings to protect components, parts, machine parts
and carbon steel structures thanks to its low cost, cathodic protection for steel. .
Galvanized coating can be obtained from a variety of methods such as electroplating,
hot dipping, spray coating, where electroplating dominates with small details, is used
in atmospheric conditions and does not require too much longevity. high.
Some of the zinc plating solutions have been studied and used such as: zinc plating
from sulfate solution, fluoride, cyanide, pyrophotphate, chloride and non-cyanide
alkali. Among them, the solutions widely used in industry are cyanide, chloride and
non-cyanide alkali.
The world's cyanide alkali-plated solution was commercialized very early in the
1960s [3]. However, recently, thanks to the introduction of new polishing additive
systems as well as due to environmental protection requirements, this plating tank is
really interested, accepted and becomes the best solution to change. cyanide plating
tank. The non-cyanide alkaline zinc plating solution has some outstanding advantages
such as: more economical, non-toxic, good coating quality, easy to pass, especially
suitable for passive solutions of Cr (III), good throwing power, especially easy to
handle wastewater [2, 4]. The downside is more complex, which requires a good
surface treatment.
However, if the alkaline plating bath is free of cyanide without additives, the poor
quality coating cannot be used in industry. Many organic and inorganic additives
introduced at relatively low concentrations can alter zinc precipitation, coating
structure, morphology, and properties. One added additive can affect many properties
of the coating, but in reality many additives are still added at the same time because
they need their synergy. They make the coating smooth, flat, increase throwing
power, have a nice gloss, work at a wide current density [3, 5-24].
In fact, in Vietnam, to meet the additive requirements for the galvanizing process
of automobile and motorcycle manufacturers, a number of additive systems have been
introduced and put into production. Since the early 2000s, ENTHONE has introduced
to the Vietnamese market the NCZ DIMENSION additive system, the COLOMBIA
company introduced the COLZINC ACF2 system, etc. However, the applicability of
these preparations is limited due to the cost. High quality has certain limitations.
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In the country, the study of additive systems for zinc plating in general and alkali
galvanizing in particular has not been given adequate attention. There is no official
research result published on the effects of these factors on the zinc plating process in
general and the non-cyanide alkali galvanizing process in particular, and no supplier
has given an additive system. for non-cyanide alkaline galvanizing tanks.
Stemming from the above domestic situation, the selection of the topic: " studying
the effects of some additives on the alkaline non-cyanide galvanizing process,
orienting the fabrication of the additive system for alkaline non-cyanide zinc
plating bath, oriented to the fabrication of the additive system for the alkaline
galvanized tank "Meeting the practical needs, the research direction can create a
product oriented application for the domestic alkali galvanizing industry, and at the
same time add insights to support the galvanizing businesses."
2. Research aims and objectives
Determining the effect of the single additive being organic and inorganic
substances such as poly alcohol, poly amines, sodium salt of various modules and the
combination of additives on the properties of the zinc coating created in the solution.
alkaline plating solution without cyanide, compare the chemical and physical
properties of the coating obtained from the non cyanide alkaline plating bath and
other plating baths. Since then, an additive system can be used in alkaline zinc-plated
tanks without cyanide
3. Main research content
1. Investigate the effects of the single additive on the throwing power capacity,
current efficiency, cathode polarization, working current density range, surface
morphology, gloss of the zinc coating.
2. Investigate the effects of the combination of additives on the throwing power
capacity, current efficiency, cathode polarization, working current density range,
surface morphology, and gloss of the zinc coating from there. an additive system that
can be used for alkaline non-cyanide zinc plating bath.
3. Determine the mechanism of action of the additives on zinc precipitation and some
properties of the coating in the alkaline non-cyanid zinc plating bath
CHAPTER 1. INTRODUCTION
In 1973, Robert Leonard Adelman and Wilmington [30] used a combination of
polyvinyl alcohol, vinyl alcohol products modified by periodic acid or sodium
perionate salt as a polishing agent for non-cyanide alkaline galvanizing baths,
improving the coating at low current density. Modified alcohols polyvinyls are also
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used with other polishing agents especially heterocyclic nitrogen compounds with at
least one substituent group to improve coating properties. In 1979, in their invention,
Zehnder and Stevens [29] used polyamin sulpho with very different concentrations
from 0.1 to 100g / liter, combined with pyrydin compounds or nicotine content of a
few g. / liter to improve galvanizing properties, in alkali-free cyanide baths. However,
pyrydin compounds are known to be very toxic volatiles, affecting the health of those
working in the surrounding environment. In recent years, there are quite a few
inventions and works published about additives for alkaline galvanized tanks [2-7,12-
21,23,26-32]. Substances used as additives for alkaline galvanizing tanks belong to
such lines as: alcohol polymers, polymers of level 1 to 4 amines, heterocyclic
compounds, surfactants, benzanaldehyde, poly alcohol or heterocyclic nitrogen
compounds have a substituent group of sulfide, reducing sugars, sodium salts, and a
number of complexing agents are used together, in each case, to improve the coating
properties, to change precipitation properties, crystal smoothing, wetting agent,
polishing agent. In general, commercial products are used well, the stability system
is not much, the system composition is quite complex, often consisting of 4
components.
In addition, a variety of other organic and inorganic additives added at relatively
low concentrations can alter zinc precipitation, coating structure, morphology, and
properties. One added additive can affect many properties of the coating, but in reality
many additives are still added at the same time because they need their synergy. They
make the coating smooth, flat, increase throwing power, have a nice gloss, work at a
wide current density [3, 5-24]