リン酸-酸化鉄-PVB系さび安定化処理法のさび非晶質化に及ぼすP, Cuの影響

抄録

Long-term atmospheric exposure of weathering steel coated with a phosphoric acid-iron oxide-PVB surface treatment for rust stabilization produces a dense, stable oxide layer. This layer is itself made up of an outer layer of rust, which includes a deteriorated treatment film, and an inner layer of rust, which is mainly amorphous rust.
Artificial (magnetite) rust testing performed to investigate the effect of PO₄^3- and Cu²⁺ on rust morphology showed that PO₄^3- has a strong amorphization effect on rust and is especially effective in oxygen-deficient environments. Cu²⁺ also has a rust refinement effect in oxygen-deficient environments, although this effect is weaker than that of PO₄^3-.
From these results, it can be inferred that the amorphous rust underneath the treatment film is formed by an reaction between Fe²⁺ produced by an iron matrix corrosion and PO₄^3- and Cu²⁺ that flow out from the treatment film in an oxygen-deficient environment. Furthermore, by acting to encourage the oxidation of Fe²⁺ to Fe³⁺, Cu²⁺ and PO₄^3- have an effect of suppressing“rust outflow”