Corrosion protection of reinforcement with phosphate coatings

Abstract

As a method of protection against corrosion, the application of phosphate coatings to the surface of steel reinforcement before the manufacture of a reinforced concrete product can be considered. The influence of modifiers introduced into the cold phosphating solution on the structure and protective properties of phosphate coatings was studied. It is established that from solutions with the addition of saccharin, glucose, Trilon A, Trilon B and washing preparations, fine crystalline, dense phosphate films are obtained. The introduction of the proposed additives also reduces the time of formation of a phosphate coating on the surface of the steel and leads to a decrease in their porosity. It has been established that phosphate coatings are resistant to the effects of aqueous, salt and acidic environments. Films deposited from modified cold phosphating solutions provide better corrosion protection compared to films obtained from a traditional cold phosphating solution. Presented phosphate coatings have high protective properties, because, due to their lower porosity, they well prevent the penetration of aggressive particles to the surface of the protected reinforcement.

White Phosphate Coatings Obtained on Steel from Modified Cold Phosphating Solutions

“…Coatings from phosphate solutions were deposited on samples of steel grade St3 (the chemical composition of steel is shown in Table 1). The surface of the samples was pre-sanded with sanding paper, degreased in 3-5% Na 2 CO 3 solution with the addition of solid soap (1-2%) at a temperature of 50-70 • C for 10 min, and etched in a 5% solution of sulfuric acid for 30 s. To obtain phosphate coatings of white color, it is proposed to additionally introduce zinc and calcium nitrates at the rate of 25-30 g/L into phosphating solutions of the composition, g/L: preparation "Majef"-35-45, Zn(NO 3 ) 2 -50-65, NaNO 2 -3-4, glycerin-1-2, trilon B-6-8, preparation OS-20-5-10 [30].…”

Obtaining Luminous Phosphate Coatings on Steel by Cold Method

“…The luminophor in the phosphate coating, when the solution is mixed, is distributed more evenly over the surface of the sample and glows brighter when developed under ultraviolet light (Fig. 2 Tests of coatings for corrosion protection by the drip method have shown that the resulting luminous coating has similar protective properties with modified phosphate coatings without luminophor [19,20] (Table 3). By the method of contact corrosion, data were obtained to determine the corrosion rate of steel samples with phosphated coatings (Table 4).…”

Effect of Modifiers Introduced into Cold Phosphating Solutions on the Physical and Mechanical Properties of the Formed Phosphate Films

“…The lower porosity and grain size of coatings deposited from modified cold phosphating solutions allows them to resist the corrosive effect of the environment on the protected surface for longer [19,20]. The time until the first signs of corrosion appear in films obtained from modified cold phosphating solutions is 2 times less than in coatings obtained by the traditional method.…”