Available online
Description
The programme examines the basic electrochemical processes involved in stress corrosion and goes on to show their significance in a practical, industrial context.
The programme examines the basic electrochemical processes involved in stress corrosion and goes on to show their significance in a practical, industrial context.
| Module code and title: | T351, Materials under stress |
|---|---|
| Item code: | T351; 10 |
| First transmission date: | 31-07-1976 |
| Published: | 1976 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:23:51 |
| + Show more... | |
| Producer: | Ted Smith |
| Contributors: | Peter Ford; Keith Williams |
| Publisher: | BBC Open University |
| Keyword(s): | Central Electricity Research Laboratories; Electrochemical processes; Industrial context; Roman buckle; Stress corrosion |
| Footage description: | Keith Williams introduces the programme. He points out the extent of corrosion on a 2,000 years old Roman bronze and iron buckle. Williams demonstrates the build up of a potential between two metals immersed in water. He uses mock-ups of a central heating system (copper pipes and steel radiators). Williams explains the reason for this potential, the dissolution reaction, with the aid of a diagram. Williams goes on to explain the process of the oxide formation reaction. He uses a diagram to help make his points. Williams, again with the aid of a diagram, discusses a problem which can be caused by the formation of hydrogen atoms at the surface of a metal (hydrogen embrittlenient) . Williams explains how to set up an experiment to induce corrosion in a stainless steel sample. He uses diagrams of the experiment to make his points. Williams performs the experiment. He supplies a changing potential to the specimen and displays the current flow ( the corrosion rate) on an oscilloscope. Williams analyses the resulting curve. An animated diagram demonstrates what happens at the surface of a stainless steel specimen when a slip step breaks the protective oxide film. Commentary be Ted Smith. Williams introduces Peter Ford of the Central Electricity Research Laboratories. Peter Ford lists the data which are necessary to have an understanding of the mechanism of stress corrosion cracking. He explains, using a schematic, an experiment which will provide some of these data. The experiment demonstrates the processes of oxide rupture, dissolution and oxide formation. Ford explains, in detail, how such an experiment is conducted. He uses photographs of the experimental apparatus to help make his points. Brief shot of an oscilloscope trace showing the results of such an experiment. An animated diagram, showing the surface of a metal, recaps the above experiment. Commentary by Ted Smith. Peter Ford examines an electropotential current density diagram as a possible basis for using these parameters to predict stress corrosion propagation rates. Ford, with the aid of a diagram, explains an experimental procedure which might be used to verify crack propagation rates. Keith Williams, with the aid of an electropotential current density diagram, sums up the programme. |
| Master spool number: | 6HT/72181 |
| Production number: | 00525_5261 |
| Videofinder number: | 1421 |
| Available to public: | no |
