2. Corrosion
• Corrosion is the gradual degradation and destruction of materials,
• usually metal
• Corrosion is caused by water and oxygen in the environment, it is
accelerated by multiple factors
• Salts in solution
• Acids
• temperature
• Presence of less reactive metal
• Working history of metal
3. Tribocorrosion
• Tribo-corrosion is the general term for any corrosion process
enhanced by flowing fluids
• Tribo corrosion is both a physical process and an electrochemical
process
• where both mechanisms act in synergy
• It occurs when a metal object is under the influence of a moving fluid and the
metal or the oxide are removed by the action of fluid
• . Even metals that normally form protective layers of oxide are at risk as the
oxide will be continually removed rather than form a protective layer.
4. Corrosion
• Corrosion is a major issue in all forms of heavy industry.
• In the oil pipeline industry in America alone, companies spent 9 billion
dollars on corrosion prevention, inspection and maintenance on 750,000
km of pipelines,
• or roughly $9 per meter.
• The National Gird comprises of a route length of over 7,200 kilometres
• The corrosion-related cost of operation and maintenance makes up 80% of
this cost
• Corrosion occurs because crude oil and natural gases contain small but
significant amounts of impurities, such as water, salts, sulphides and
particulates.
5. Natural Gas and Pipelines
• Pipeline are used to cheaply transport liquids very large distances in
large quantities
• Almost half of UK mains are still made of cast iron.
• The expansion of non-conventional gas means Transmission networks
will have to deal acidic gas that they were not designed to handle
• Even the Polyethylene pipes are nearing the end of their working lives
in some places.
6. Pipelines and new corrosion issues
• Sour hydrocarbon: Oil that contains Sulphuric Acid, potentially
releases H2S
• Acidic hydrocarbons : Contains Sulphuric acid, Carbonic Acid (CO2)
and Naphthenic Acid
• Asphaltenes and diluted bitumen: Oil that is very viscous and
requires heat and pressure to move it along.
• Sand and particulates in oil, even within the distribution network, the
gas velocity is limited to 20m/s due to gas dust and vapour.
7. Corrosion Simulation
• Not feasible to constantly monitor all pipeline network
• Corrosion rates are found experimentally, and used to predict where
damage will occur
• Also used for design, extra thickness is added to parts where corrosion will
occur
• A sample of the metal, a corrosion coupon, is then placed in the
simulated environment for a set amount of time. The corrosion
coupon is them removed from the environment and the corrosive
effects are measured.
8. Impingement rig
• Sprays a solid jet of oil upon a
sample of metal.
• The fluid impinges upon the
metal coupon at an angle or
perpendicular to it.
• The oil velocity can be varied
• The oil can be pure oil, or have a
mixture of oil and water
• The water can be a salt solution
• The oil can contain solids
suspended
9. Design
• The test rig was based on pre-
existing impingement rig
designs
• An oil-water mixture was to be
pumped through a nozzle and
impinge upon a test probe or
corrosion
• The experiment has to be built
materials and equipment that
was found and salvaged within
the aero lab
10. Viewing box
• Perspex was used due to its chemical
resistance, hardness and transparency.
• 2 sheets of one cm thick Perspex were
acquired from old spare parts of a wind tunnel.
• Sides of the box were held together by
screws
• Edges were sealed with silicone, the
silicone layer was covered by resin to
prevent chemical damage to the silicone
• Box is reinforced by a frame
11. Pump
• A pump at the back of the aero lab was resourced.
• Pump was very old, it needed a lot of electrical parts replaced
• Several weeks were wasted waiting for orders for parts to be fulfilled
• Piping was set up to pump oil though the nozzle and onto the jet
12. Nozzle
• Once the pump was working, it was possible to calculate the flow rate
of the pump
• The flow rate was used to calculate the size needed of the nozzle
orifice to get a speed consistent with literature requirments
• . Using a standards ASTM G-73, a speed of 60m/s was needed
13. Oil
• For the base oil, the commercially available hydraulic oil Hydrol VH 32
was used
• The oil was chosen as it was cheap and has a good tolerance of heat
and pressure.
• The experiment started with pure oil to provide a control, and to
examine the effects of the fluid impinging on its own
14. Corrosive additives
• A solution was made to simulate ground water within a typical sour
crude oil reservoir
• A compositional analysis was provided by Dr Akanji
• A the salts were dissolved in a 25% v/v solution of Sulphuric acid
• Salts include NaCl, CaSO3.H2O, KCL, NaHCO3
• 10g of Poly anionic Cellulose was added as an emulsifier
15. Corrosion Coupon
• these are of a predetermined shape, and a carefully measured weight
and thickness and are made from the material being tested
• The coupons are cleaned with a solvent and sandpaper to remove all dirt and
oxide
• The starting mass is measured and pictures taken under a microscope
• The coupon is then placed in the test rig for 200 hours
• The coupon is re-cleaned and the final mass taken. Pictures of the coupon
under the microscope are retaken and compared, Vickers hardness tests are
also done
• For the is experiment, the coupon was cut to 100mm by 150mm out
of 5mm cold-rolled mild steel.
• The coupons material can be changed or coatings used in later
experiments
16. Testing
• Two experiments were ran
• The first was a control with pure oil and no water or acid
• The second had oil with 2% acid and a salt fraction in emulsion
• The first test ran for 200 hours,
• The second test only ran for 2 hours before the pump failed
• Experiment ran perfectly otherwise
17. Results
• The first coupon showed no damage, it had no mass loss to one
hundredth of a gram
• The second coupon was only in the rig for a couple hours, it was
thought that under such a short time, there would be very little mass
change, and it would not give an accurate average.
19. Coupon 2 before the Test x10
Coupon 2 after the test at x10 note the
Vickers hardness test
20. Coupon 2 after the test at bare area
X200
Coupon 2 after test at heavily rusted
area x200
21. Future work
• The rig itself held up to the oil very well
• The pump can be replaced and the experiments continued
• The pump, piping and nozzle are all designed to be replaceable.
• The tests were mere a proof of concept, a working impingement rig
has a lot of potential for further research
