Yoshikazu Miyata

Galvanic Series of Metals Conventionally Used in Tap Water With and Without Flow and Its Comparison to That in Seawater

Abstract Galvanic series of 17 metals often used in aerated tap water was determined by measuring corrosion potential. Experimental conditions were selected in considering such systems as water supply, water cooling, water heating, and water condensing. Galvanic series in seawater is easily obtainable. However, very little data on galvanic series in tap water are available in spite of its importance in life lines. The authors found that the time changes of corrosion potential could be classified into five types depending on metals. Galvanic series in tap water was compared to that in seawater. Effect of flow is also discussed. The main results in tap water are that the potential of aluminum does not settle down; the position of stainless steel and copper alloys including pure copper is reversed by applying the flow; the potential of lead is more active than in seawater in contrast to the other metals; the potential differences between stainless steels and copper alloys including pure copper is much smalle...

Influence of Chloride Ions on Corrosion of Modified Martensitic Stainless Steels at High Temperatures Under a CO2 Environment

The influence of chloride ion concentration on the passivation film and corrosion product film of martensitic stainless steels (SS) (13% Cr, modified 13% Cr-1% Mo, modified 13% Cr-2% Mo, and 15% Cr...

Corrosion Behavior of Spheroidal Graphite Cast Iron with Different Carbon Contents in Sulfuric Acid Solutions

Corrosion behavior of spheroidal graphite cast iron with different carbon contents has been studied. Immersion tests and electrochemical measurements were performed in sulfuric acid solutions of pH from 1.0 to 3.0. The corrosion current density of the cast iron is not a function of the content of carbon and the area of graphite particles at the surface. The corrosion current density of the cast iron is higher than the reported values of pure iron. This results from the promotion of both the anodic and cathodic reactions. The dependences of the corrosion potential and the corrosion current density on pH are the same as those of pure iron.

Anodic Dissolution of Spheroidal Graphite Cast Iron with Different Pearlite Areas in Sulfuric Acid Solutions

The rate equation of anodic dissolution reaction of spheroidal graphite cast iron in sulfuric acid solutions at 298 K has been studied. The cast irons have different areas of pearlite. The anodic Tafel slope of 0.043 V decade−1 and the reaction order with respect to the hydroxyl ion activity of 1 are obtained by the linear potential sweep technique. The anodic current density does not depend on the area of pearlite. There is no difference in the anodic dissolution reaction mechanisms between pure iron and spheroidal graphite cast iron. The anodic current density of the cast iron is higher than that of the pure iron.

Relationship between Corroded Area and Corrosion Potential in the Initial Stage of Corrosion of Steel in Aqueous NaCl Solution.

酸素を含むNaCl水溶液中の鋼の腐食初期過程では,鋼の表面に,腐食している部分と金属光沢が保持されている部分が存在する。腐食している部分の面積は時間とともに増加する.被覆率(θ)を全表面積(A)に対する腐食面積(Aa)の割合と定義し[θ=(Aa/A)],25℃ における腐食電位(Ecorr)とθの関係を調べた。その結果に基づいて,鋼表面上で生じる電気化学反応について議論した。腐食初期過程では,Ecorrと10g[θ/(1-θ)]の関係はNaClの濃度やpHに依存せず,傾きが-130mV/decadeの直線となった.この結果は,次の(a),(b)の仮定により説明できた。(a)腐食生成物が堆積している部分でアノード反応が生じ,金属光沢が保持されている部分でカソード反応が生じている。(b)アノード反応速度は電位に依存しない.腐食初期過程では,アノード反応支配で腐食が進行すると考えられる。