Corrosion of Zn under acidified marine droplets

Atmospheric corrosion of Zn under a variety of simulated marine aerosols was studied. In-situ monitoring of droplet pH, volume loss measurements, identification and distribution of crystalline and amorphous phases from corrosion under different droplets were used to understand the role of acidification on atmospheric corrosion of Zn. Results for various droplet chemistries are discussed in terms of initiation mechanism, phase distribution and surface morphology in conjunction with chemical equilibrium calculations. Zn exposed to sulphate containing droplets had relatively small corrosion rates and greater coverage with Gordaite as compared to sulphate-free droplets where coupons have relatively more coverage with Simonkolleite.No Full Tex

Multiscale modelling of the corrosion of metals under atmospheric corrosion

This paper describes a multiscale (from global to micron) model for the prediction of atmospheric corrosion. The model has a modular structure, in which the higher scales set the boundary conditions for the lower scales, and the lower scales alter some of the constants in the upper scales. The model has primarily been designed for Australian conditions and so focuses on corrosion by marine aerosols. The upper level modules look at aerosol production by oceans and surf beaches, salt transport and deposition, and cleaning events such as rain and wind, to provide an estimate of salt retention on surfaces. Separate modules that define surface temperature, surface relative humidity, and wetting and drying of deposited hygroscopic salts, enable the prediction of the (three-hourly) ‘state’ of a surface, where ‘state’ is defined as dry, wet from rain or wet from the wetting of hygroscopic salts. The state model is combined with a damage model to estimate the progression of damage with time. Currently, damage models are either probabilistic (define the occurrence, growth or death of pits as probability functions) or empirical (define a single relationship between mass loss in a given state on the basis of measured data) in nature, but new experimental and modelling research is being undertaken to develop first-principle models of corrosion under established oxide films.No Full Tex

A high-throughput test methodology for atmospheric corrosion studies

This letter presents a high-throughput methodology to systematically study individual variables involved in atmospheric corrosion. Corrosion caused by droplets, representative of various atmospheric environments, was quantified in terms of volume loss as measured through optical profilometry. Measurements were sensitive to variations in electrolyte chemistry and allowed relatively rapid and reproducible discrimination between the effects of different atmospheric parameters. This approach allows a high degree of experimental control and calculated corrosion rates from optical profilometry were comparable to those obtained using an independent electrochemical method.No Full Tex