Rustposities

Rustposities is a term used in materials science to describe discrete locations on a metal surface where rust formation concentrates during corrosion. The term appears in some Dutch-language corrosion literature and is used to denote localized rusting sites that differ from uniform surface oxidation.

Definition and scope: A rustpositie is a localized zone where iron oxide and related corrosion products accumulate preferentially, often appearing as pits, blisters, or small clusters. They reflect underlying heterogeneities in the metal or environment that create micro-galvanic areas.

Causes and formation: Rustposities arise from surface roughness, inclusions, grain boundaries, phase boundaries, or coating defects that disrupt uniform protection. Environmental factors such as gradients in oxygen, humidity, chloride concentration, and electrolyte flow promote localized anodic or cathodic activity, concentrating rust in specific spots. Galvanic coupling between different phases or localized stress can also drive rustposities.

Detection and analysis: Identification relies on microscopy (optical, SEM) and spectroscopy (EDX, XPS, Raman) to map composition. Microelectrochemical techniques and corrosion mapping enable spatially resolved measurements of current density and growth rates at rustposities.

Significance and applications: Understanding rustposities helps diagnose corrosion behavior, assess the effectiveness of protective coatings, and guide alloy selection and maintenance strategies. They are particularly relevant for predicting pit initiation and the progression of localized corrosion.

Limitations and terminology: The usage of "rustpositie" is not universal; readers should confirm its definition in the source. See also corrosion, pitting corrosion, localized corrosion, rust.