In situ corrosion of canister materials in bentonite: the IC-A experiment at Mont Terri

Since 2012, a long-term in situ corrosion experiment (IC-A) has been conducted in the Mont Terri Underground Research Laboratory in Switzerland. The aims of the project with international partners are to confirm the long-term anaerobic corrosion rate of carbon steel and copper in compacted bentonite under repository-relevant environmental conditions, to gather in situ corrosion data supporting canister lifetime predictions, to provide confirmation of the effect of the bentonite buffer on microbial activity and microbially influenced corrosion, and to study the effects of welding (steel) and deposition technique (copper) on the corrosion properties of these candidate materials for disposal canisters. To date, carbon steel and cold sprayed and electrodeposited copper coatings have been retrieved after different exposure periods up to 3 years and characterised to establish the composition of the corrosion product, the morphology of the corroded surface, and to measure the rate of corrosion. For carbon steel specimens, a complex corrosion product was identified, consisting predominantly of magnetite. Low average anaerobic corrosion rates were measured for carbon steel and a very modest amount of alteration was identified on copper. The density and the initial form of the bentonite had a small influence on the rate of corrosion, across all materials.

High-Performance Methods for Welding Steel P460NL2

The article discusses comparative test results concerning two welding methods, i.e. SAW and MAG. The tests involved the making of welded joints in steel P460NL2, the verification of the chemical composition of supplied steel, the comparison of the quality of joints (in accordance with PN-EN ISO 5817) as well as the performance of macroscopic tests and the comparison of mechanical properties and hardness.

Bonded CFRP/Steel Systems, Remedies of Bond Degradation and Behaviour of CFRP Repaired Steel: An Overview

This literature review has examined the use of FRP composite materials as a potential retrofitting technique for civil structures. Importantly, the various material properties, bond mechanisms, durability issues and fatigue resistance have been discussed. Studies exploring the performance of CFRP repaired steel have strongly indicated its potential as a rehabilitation material. These systems offer many improvements over the current bulky and less chemically resistant methods of bolting or welding steel plate patches. This review has established and highlighted the factors that affect CFRP/steel bond durability, namely surface preparation, curing, corrosion, fatigue loading, temperature and moisture ingress through studies that focus on their effect. These studies, however, often focus on a single influencing factor or design criteria. Only limited studies have investigated multiple parameters applied simultaneously, even though they commonly occur together in industrial practice. This review aimed to summarise the numerous influencing parameters to give a clearer understanding of the relevance of CFRP repaired steel structures.

Combined-cycle corrosion testing of steel/6000 series aluminum alloys joined by friction welding

Tailored blanks, especially semi-finished parts formed by welding steel and aluminum alloys, are being employed in the automobile industry to reduce the weight of automobiles. However, when dissimilar metals are welded, galvanic corrosion due to differences in ionization tendency occurs, decreasing the reliability of such welded products. In addition, the heat input when aluminum alloys are welded causes an aging problem. In this study, combined-cycle corrosion testing was performed for S45C/6000 series steel/aluminum alloys joined by friction welding. First, S45C steel pipes were joined to A6061-T6 and A6063-T6 aluminum alloy pipes by friction welding. Then, after combined-cycle testing, changes in appearance and joint strength were investigated as the number of cycles increased. In the natural aging test, test pieces were placed in a desiccator whose temperature was adjusted to about 20 °C with a humidity from 0 to 10 %. One piece was removed at predetermined time intervals and used in tensile testing. After tensile testing, fracture surfaces were observed with an optical microscope. For the S45C/A6061 friction- welded material, a decrease in tensile strength was found at the 36th cycle. It was confirmed that the strength of the S45C/A6063 friction-welded material decreased clearly at the 27th cycle. Any obvious changes in strength were not seen in specimens after 540 hours of natural aging.

Evaluation of resistance of silicone sealant to ultralow temperature effect

Properties of the silicone sealant VGO-1 have been examines, which is used for production of glue-welded joints made by contact welding. Conditions to produce glue-welded joints are described. It was found out that when welding steel specimens of the 08kp brand on the VGO-1 sealant there was a decrease in a welding current value and an increase in welding time and the electrode compression force. The study of sealant structures after storage at different temperatures demonstrated that the used sealant had good resistance at –30 °С in the air environment and satisfactory resistance at –50 °С in a liquid environment. The swelling index of the sealant after 20 day storage in medicinal ethyl alcohol was no more than 4.5%.

EVALUATION OF COATINGS TENDENCY TO THE PORES AND NON-METAL INCLUSIONS FORMATION IN A WELD

The task of welding steel elements painted with various coatings is found in a number of industries at the stages of factory assembly and installation of large-sized structures, as well as during repair and restoration work. The porosity of the welded metal is the most common defect in electric arc welding without removing the coating, and the tendency to pore formation is a normalized parameter in the certification of interoperable primers (EN ISO 17652-2: 2003). The studies carried out cover wide-spread polyacrylate, alkyd, epoxy, polyvinyl butyral primers in an extended working thicknesses range. In addition, the evaluation technique is used for zinc-filled and organosilicate protective coat-ings. Based on the study of the nonmetallic inclusions composition in a weld by energy dispersive X-ray spectroscopy and using a scanning electron microscope, the behavior features of the coatings de-struction products and their derivatives during physical and chemical transformations under welding are described. The technological features of welding without coating removing are noted: stability of the mode parameters, resistance to metal spraying and coating burnout activity in the areas adjacent to a weld.

General Considerations Regarding Friction Stir Welding of some Steels Used in Important Industrial Fields

The paper present some general aspects regarding results obtained by ISIM Timișoara at FSW of steel alloys, with wide use in important industrial fields. The paper also contains information on own contributions of ISIM Timișoara in the field of FSW.Until the present, ISIM Timisoara has responded to some specific requests from the industry, for applying of the FSW process to light alloys and industrial copper Cu 99.The paper presents some general elements regarding the results obtained to welding steels having wide use in industry and which can substantiate industrial applications.The experimental welding programs were developed using the techniques of application of the FSW process, made by ISIM Timisoara: FSW welding machine, welding tools for steels, monitoring systems of the welding process FSW, respectively system for applying of the FSW-TIG hybrid welding process.Sintered tungsten carbide P20S tools with smooth shoulder and pine in 3 constructive variants: smooth conical, smooth cylindrical and pine with four flat recesses (pyramid trunk) were used.It has been shown that the welding tools made of P20S tungsten carbide, with sharp edges, are more resistant and present the best solution for FSW applications.Experimental programs have shown that by observing specific process conditions, the FSW process can be applied with excellent results when welding steel.