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Register a new userCorrosion of Austenitic Stainless Steels in Industrial Phosphoric Acid
تآكل بعض خلائط الفولاذ المقاوم للصدأ ذي البنية الأوستنيتية في حمض الفوسفور الصناعي
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أظهر البحث الأهمية الكبيرة لمتابعة دراسة تأثير حمض الفوسفور المشوب المنتج في الشركة العامة للأسمدة في الخلائط المعدنية ذات المقاومة العالية للتآكل، و ذلك للتوصل إلى خلائط مناسبة للتجهيزات و الآلات المعدة لإنتاجه نظراً إلى تعرض هذه الأخيرة لمعدلات التآكل العالية التي تقود إلى مشكلات تآكلية كبيرة و خروج جزء من هذه التجهيزات و الآلات من الخدمة.
This research showed the great importance for following studies of the effect of polluted phosphoric acid, produced in General Fertilizer Company, on the high corrosion resisting alloys, to reach suitable alloys for equipments and machines used for its production, because of its high corrosion rates that create many corrosion problems in these equipments and machines.
References used
Enrico Pelitti- C&I/ Girdler INC, Corrosion and material of construction at phosphoric acid. chapter 10
G.Kleinman, Fluorine Recovery – Swenson Symposium on Wet-process phosphoric Acid, Tampa, Fla. March 1965
E.I. Du pont de Nemours and company, Inc., 1978, Hydrofluoric Acid, "Technical Bulletin
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Welded joints corrosion phenomena for some kinds of stainless steels and nickel alloy was studied in
polluted phosphoric acid 37.7%H3Po4 using electrochemical techniques like Tafel polarization. Corrosion
rate of base metal and weld metal had calcu
lated & compared among these alloys.
Laboratory Test results showed the change in both corrosion rate and corrosion current densities (Icorr)
for tested alloys, and there is a clear difference between base metal and weld metal in most of tested alloys
, which lead to high corrosion rates of welded joint, and change in its properties then gets out of service in
some service conditions. The stainless steel 904L has low corrosion rates and low difference in corrosion
rates between base metal and weld metal, so it may be the most suitable alloy, among all the studied
alloys, for exploitation in polluted phosphoric acid 37.7%H3Po4 produced at the General Fertilizer
Company in Homs city.
The corrosion behaviour of plain-carbon steels in water environments has been studied. In
this study, a wide range of carbon steels are used in the most common corrosion environments
which are salt water and drinking water. The specimens were immer
sed in the water media and corrosion rates evaluated, using the weight loss method. The effect of
carbon content, corrosion environments and time of immersing on the specimens corrosion
rates of Hypo-eutectoid plain carbon steels have been studied. The aim of this work is to study
the effect of carbon content on the corrosion rate of carbon steels in different corrosion media
and various time intervals. The obtained results showed that there is a clear correlation with
the microstructure where higher Pearlite show higher corrosion rate, so the corrosion rate
increases with the carbon content. The results also show that the corrosion rate of carbon-steel
in salt water is higher than its value in drinking water. It is also found that longer exposure
time, leads to a lower corrosion rate while weight loss is still increasing.
The thickness of the diffusion layers was studied, along with the phases and the microstructure and
composition, across the depth in diffusion zone. The obtained results proved the effect of nitriding
system in the growth of the diffusion layers on
surface of double composite martensitic - austenitic alloy
steel.
Analysis of mechanical and tribological characteristics of treated double composite steel under dry
friction was also studied. It was found that diffusion treatment had a significant influence on work
capacity of tested alloy. Stability of alloy after nitriding was (2.5-4) times higher in magnitude
compared to untreated alloy.
فولاذ سبائكي ذو بنية مركبة
تقسية و إرجاع
نتردة غازية
بنية و تركيب طوري
طبقات انتشارية
قساوة سطحية
خواص ميكانيكية و تريبولوجية
Double composite alloy steel
hardening and tempering
gas nitriding
diffusion layers
microstructure and phase composition
surface hardness
mechanical and tribological properties
المزيد..
Design of experiments (DOE)
had been used in the study, and the results had been evaluated by the
surface response method. The results showed that the welding
current is the main parameter by its effect on the mechanical studied
properties and the parameters values which give the best responses
had been determined.
The aim of this work is to study the effect of the aging heat treatment on the pitting corrosion resistance of martensitic stainless steel. In this research a number of specimens from martensitic stainless steel were subjected to solution treatment a
t 1050 for one hour followed by water quenching then aging in the temperatures range (400-750) for different holding times (1-16 hrs).
After heat treatment, two types of corrosion tests (accelerated test and immersion test) were conducted. The results obtained in this research showed that the pitting corrosion resistance was
affected by Aging temperature and three critical temperatures were found in corrosion test: the
specimens aged at 475 0C had maximum corrosion rate. This may be due to the presence of stringer δ-
ferrite and precipitation of very fine precipitates which precipitated heterogeneously in the martensitic
matrix, which led to an increase in corrosion rate. The specimens aged at temperatures range (550 – 625) 0C had minimum values of corrosion rate, this is attributed to the high volume fraction of retained austenite. The specimens aged at temperatures above 625 had intermediate corrosion rate.
The type of pits, which resulted from two pitting corrosion tests, was independent form the form of δ-ferrite and carbides which presence in microstructure.
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