Retrieval and analysis of coupons from the 1 year module pair

macote coupon 1 year 001

Modules are removed using a specially designed capture tool and inserted into argon filled transport flasks. The top of the borehole is continually injected during the removal process to prevent air from entering the borehole whilst the double packer system is out of the borehole.

macote coupon 1 year dismantling 

Careful dismantling, dissection, and removal of metal coupons in the glove box.

 

CHARACTERISATION OF METAL COUPONS

Postmortem characterisation of the coupons (Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis) was carried out at the University of Oxford. Weight loss measurements were carried out at Jacobs Harwell laboratories. Profilometry was carried out at the University of Manchester.

 

AVERAGE CORROSION RATES

macote coupon 1 year corrosion rates

The corrosion rate of carbon steel ranged from 1.87 μm year−1 to 2.05 ± 0.05 μm/year, while the corrosion rates for the copper coupons were much lower and the corrosion rate of stainless steel was negligible. At a bentonite density of 1250 kg / m3, the cold‐sprayed copper had an average corrosion rate of 0.17 μm / year while the electrodeposited and wrought copper had an average corrosion rate of 0.24 μm / year. The corrosion rates did not significantly vary with bentonite density. So far there was no evidence of material loss due to microbially induced corrosion.

 

PROFILOMETRY MEASUREMENTS

macote coupon 1 year profilometry

Profilometry measurements for pristine coupons and coupons after one year exposure. For all metals, the roughness after exposure was similar to those of pristine samples, indicating that pitting or surface roughening did not occur or was minimal.

The GTS underground facilities are also available to interested 3rd parties for underground testing and research. The GTS offers cost-effective access to a fully developed, well characterised underground research facility with round the year logistical support - please contact Dr. Ingo Blechschmidt, Head of the Grimsel Test Site, for further details.
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