Introduction
St-37 is one of the most popular types of steel, which has been widely used in many industrial applications due to its proper mechanical properties. However, the use of this type of steel has been restricted for many applications due to its low corrosion resistance [1,2]. Many different methods have been utilized in order to protect the steel structures against corrosion. Among them, conversion coatings and organic paints have been widely utilized to increase the corrosion resistance of the metal substrates [3–5].There are different kinds of conversion coatings which have been applied on the steel substrates to protect them against corrosion and enhance the organic coatings’ adhesion properties. Among them, phosphate based conversion coatings are the most common type of chemical treatments which have been applied on the steel substrates [6–8]. Applying these types of chemical treatments on the steel surface led to the increase of the corrosion resistance of steel and the increase of the organic coatings’ adhesion to the metal surface. Surface treatment of steel bodies by zinc phosphate conversion coatings has been considered as a useful surface preparation method to increase the corrosion resistance of the steel [9]. Also,they are useful adhesion promoters for paint, varnish and lacquer.It has been also shown that the phosphate coatings can also provide some protection against under-paint corrosion [10–13] However,the phosphate coating is porous and contains some micro cracks and because of these it cannot provide high corrosion resistance for the steel substrate. Chromates have been used as sealing agent for phosphate layers to enhance its corrosion resistance [14]. There-fore, dipping phosphates samples in the chemical bath containing hexavalent chromium has been a common and promising method to obtain a surface with less porosity and higher corrosion resistance. Also, the under-paint corrosion protection of the phosphate coatings can be significantly enhanced when the phosphate coated metal is post-treated with a dilute acid chromate rinse solution before paint application. However, due to toxic and carcinogenic nature of the chromate based conversion coatings, the use of these coatings has been extremely restricted in last decades
แนะนำSt-37 is one of the most popular types of steel, which has been widely used in many industrial applications due to its proper mechanical properties. However, the use of this type of steel has been restricted for many applications due to its low corrosion resistance [1,2]. Many different methods have been utilized in order to protect the steel structures against corrosion. Among them, conversion coatings and organic paints have been widely utilized to increase the corrosion resistance of the metal substrates [3–5].There are different kinds of conversion coatings which have been applied on the steel substrates to protect them against corrosion and enhance the organic coatings’ adhesion properties. Among them, phosphate based conversion coatings are the most common type of chemical treatments which have been applied on the steel substrates [6–8]. Applying these types of chemical treatments on the steel surface led to the increase of the corrosion resistance of steel and the increase of the organic coatings’ adhesion to the metal surface. Surface treatment of steel bodies by zinc phosphate conversion coatings has been considered as a useful surface preparation method to increase the corrosion resistance of the steel [9]. Also,they are useful adhesion promoters for paint, varnish and lacquer.It has been also shown that the phosphate coatings can also provide some protection against under-paint corrosion [10–13] However,the phosphate coating is porous and contains some micro cracks and because of these it cannot provide high corrosion resistance for the steel substrate. Chromates have been used as sealing agent for phosphate layers to enhance its corrosion resistance [14]. There-fore, dipping phosphates samples in the chemical bath containing hexavalent chromium has been a common and promising method to obtain a surface with less porosity and higher corrosion resistance. Also, the under-paint corrosion protection of the phosphate coatings can be significantly enhanced when the phosphate coated metal is post-treated with a dilute acid chromate rinse solution before paint application. However, due to toxic and carcinogenic nature of the chromate based conversion coatings, the use of these coatings has been extremely restricted in last decades
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