Alloys corrosion rates

This element has proved to be most effective for reducing the corrosion rate of lead—antimony alloys and has therefore been intensively studied [17,30—32]. Alloy corrosion rate (evaluated by weight loss) and electrode potential have been measured vs Ag content for Pb—Ag and Pb—Sb—Ag alloys [33]. The obtained curves are presented in Fig. 4.14. 

Bundy, K. J., "Modification of Surgical Implant Alloy Corrosion Rates by Static and Dynamic Loading, Extended Abstracts NACE Corrosion Research Symposium, 1989, pp. 61-64. 

Bundy, K. J. and Amey, M. M., "Polarographic Determination of Released Ion Valence States and Implant Alloy Corrosion Rate Accuracy, Transactions of the 15th Annual Meeting of the Society for Biomaterials, 1989, p. 53. 

The LPR probe alloy multiplier should be used when electrodes are made from materials other than carbon steel. The purpose of the multiplier is to convert the built-in constants that are specific for carbon steel to other alloys. Corrosion rate multipliers account for the specific alloy s anodic reactions, the valency of the anodic reactions, the alloy equivalent weight, and the alloy density. LPR electrodes should be changed periodically and at least annually. 

In most metals and alloys, corrosion rates increase with increased velocity, but a marked increase is experienced only when a critical velocity is reached. 

Alloy Corrosion Rate per year mils mm Number of Attacked Crevices Maximum Depth of Crevice Attack, mils mm... 

The impurity effect is a special case of a second phase accelerating the corrosion of a Mg alloy. It warrants separate treatment because it is important and is wholly negative. Four impurity elements (Fe, Ni, Cu and Co) were found by Hanawalt et al. [50] to have a large accelerating effect on saltwater corrosion of Mg binary alloys. Corrosion rates were accelerated 10-100-fold when their concentrations were increased [51]. These impurity elements have extremely deleterious effects because of their low solid-solubility limits in a-Mg and their abilities to serve as active cathodic sites [52]. When their concentrations exceed their tolerance limits, they serve as active catalysts for electrochemical corrosion [53]. For each of these elements a tolerance limit can be defined as illustrated by Fig. 3.17. When the impurity content exceeds the tolerance limit, the corrosion rate is greatly accelerated, whereas, when the impurity content is lower than the tolerance limit the corrosion rate is low. 

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