# Erosion Corrosion of Titanium Specimen

1. Apr 5, 2009

### bill nye scienceguy!

1. The problem statement, all variables and given/known data

Seawater at 13m/s containing 1750mg/L sand impinges on a 8cm$$^{}2$$ titanium specimen. I'm given a polarisation curve (which I'm unable to reproduce here for the moment) and the data that without cathodic protection a weight loss of 4.0mg is measured in 16 hours and with CP the specimen loses 2.8mg in an equivalent time period.

The problem asks me to use this data, along with information derived from the polarisation curve (which also has curves for quiescent water and clean water at 70m/s) to calculate the proportions of total weight loss attributable to each of pure corrosion, pure erosion and synergy effects.

2. Relevant equations
Nernst Equation?

3. The attempt at a solution
Taking from the polarisation curve a value of i$$_{}corr$$ to be 20$$\mu$$amps, I calculated, using Faraday's Law, that in the non-CP condition 0.19mg Ti will be lost to pure corrosion.

Given that I know the weight that will be lost due to only erosion and synergy (assuming CP to be 100% effective in this case) to be 2.8mg, how do I calculate the amount of weight lost due to erosion alone?

My general method was to calculate how much is lost to erosion as it will be the same in both cases, calculate the corrosion loss in the non-CP instance since I don't have any data relating to the method of CP employed and take the amount due to synergy to be the remainder of the 4.0mg of the original data set.

Should I assume, then, that 1 sand particle dislodges x amount of Ti and work from there? Or should I be doing something completely different? Help much appreciated!

(I started a similar, generalised thread in the Mechanical Engineering forum , hopefully this is specific enough not to warrant deletion.)