Abstract
The anodic behavior of coldrolled lowcarbon steel in the aqueous STPP solution with aluminum hydroxide, borax, and glycerin additives at room temperature has been studied. It was revealed that the potentiodynamic curves that characterize the anodic behavior of steel st05kp samples show s up to three passivation plateaus. Additionally, the anodic curve ends with the complete passivation plateau with an anodic current density equal to zero. The obtained results demonstrate realization of the stepwise formation mechanism of tripolyphosphate coat in the 12 % aqueous STPP solution with additives. It was found that with the addition of 2 % Al(OH) 3 , a narrowing of the first passivation plateaus is observed. The addition of glycerin shifts the potential of passivation plateau formation toward negative values by about 150 mV. When borax was added, only the complete passivation plateau is present on the anodic curve. It was established that in the STPP solution with the addition of aluminum hydroxide, glycerin, and especially borax, steel passivation occurs earlier than in the solution without additives. This indicated the acceleration of tripolyphosphate coat formation when additives are used. The absence of the first two passivation plateaus on the anodic curve that describes the coat formation in the STPP solution with the borax additive indicated that formation occurs at the highest rate. In the process of studying the anodic behavior of steel st05kp with the formed coats, in 0.1 N Na 2 SO 4 , it was found that the coats formed in the aqueous sodium tripolyphosphate solution with additives possess protective properties. The greatest positive effect on protective properties of the coats is provided by aluminum hydroxide. Based on the results of combined studies, it was established that aluminum hydroxide can be recommended as the most effective additive for improving protective properties of tripolyphosphate coats. Borax can be recommended as an additive that accelerates coat formation.
Highlights
Conversion coatings are the most economically viable method for protecting metals against corrosion, which is used in various fields, including automobile and aerospace industries [1,2,3,4,5,6,7].Currently, metal goods manufacturers aim to decrease usage of toxic chromates and nitrites conversion coatings for corrosion protection during in-between operation and long-term storage.Development of new non-toxic, effective and relatively cheap compositions is a relevant problem in the field of metal corrosion inhibition.Polyphosphates are of particular interest for such compositions
As a result of the analysis, it is proposed to study the influence of aluminum hydroxide, borax, glycerin on the formation of tripolyphosphate coats on steel in the aqueous Sodium tripolyphosphate (STPP) solution, with high protective properties
It was established that the formation of coats in the STPP solution with additives, occurs step-wise
Summary
Conversion coatings are the most economically viable method for protecting metals against corrosion, which is used in various fields, including automobile and aerospace industries [1,2,3,4,5,6,7].Currently, metal goods manufacturers aim to decrease usage of toxic chromates and nitrites conversion coatings for corrosion protection during in-between operation and long-term storage.Development of new non-toxic, effective and relatively cheap compositions is a relevant problem in the field of metal corrosion inhibition.Polyphosphates are of particular interest for such compositions. Conversion coatings are the most economically viable method for protecting metals against corrosion, which is used in various fields, including automobile and aerospace industries [1,2,3,4,5,6,7]. Metal goods manufacturers aim to decrease usage of toxic chromates and nitrites conversion coatings for corrosion protection during in-between operation and long-term storage. Development of new non-toxic, effective and relatively cheap compositions is a relevant problem in the field of metal corrosion inhibition. Polyphosphates are of particular interest for such compositions. In comparison to other compounds, the main advantage of polyphosphates is their low toxicity. Polyphosphates are able to inhibit corrosion and salt deposition even at low concentrations
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