bolbol
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Role of dichromate in phosphoric acid rust removing solutions?
I was looking at a famous rust removing/converting solution and when I was looking at the ingredients, along with phosphoric acid it also mentioned
dichromates.
Is there any importance to the presence of dichromates? I plan to rust proof the frame of my car and I will just be using phosphoric acid by itself so
I want to know if there would be any benefits of having dichromates in there
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Porphyrin
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Dichromates are rust inhibitors by means of creating a passivation layer on the steel.
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bolbol
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Would the passivation layer be iron chromate?
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Porphyrin
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Yes, I believe so.
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agent_entropy
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The main function of chromates or dichromates as corrosion inhibitors is to repair defects in and thicken the native oxide layer (passivation layer)
on the surface of the metal. Depending on the alloy a secondary inhibition mechanism may come into play where a film of chromate is formed which
provides a ready source of chromate to repair any further damage to the oxide film.
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