Suppressing corrosion Cathodic protection example: protecting ship plate
Suppressing corrosion Cathodic protection example: protecting hot water heater tanks
Suppressing corrosion Cathodic protection Problem: steel fermentation tank in brewery sacrificial anodes add metallic ions to electrolyte
Suppressing corrosion Cathodic protection Different approach: Impose a voltage across cell formed by tank (cathode) and an inert anode choice of anode material: very inert material like Pt but oxygen gas produced at anode
Suppressing corrosion Cathodic protection Different approach: Impose a voltage across cell formed by tank (cathode) and an inert anode choice of anode material: use carbon - inert C + O2 CO2
Suppressing corrosion Cathodic protection "…..join in a planned discussion of whether it is best to use copper tubing coils or stainless steel tubing coils inside of a stainless steel beer fermenter, the coils being used as a chiller? There has been a discussion in another brewing forum about competing concerns between the two, i.e., copper conducts heat better and is easier to bend, versus copper will slowly dissolve in the acidic environment of beer"
Suppressing corrosion Use passivated materials Ni - NiO Ti - TiO2 Al - Al2O3 COR-TEN: 0.19% C 0.30% Cu 0.40% Ni 0.50% Cr 0.05% V
Suppressing corrosion Anodizing Al & other materials can be anodized very thick oxide coating formed (8-50 microns)
Suppressing corrosion Thinking again of noble metal coatings, what about Cr plating? 540x 2300x Cr plating usually filled w/ microcracks due to stresses in plating
Suppressing corrosion Cr plating frequently a series of layers
Corrosion examples in shuttle mat'ls
Corrosion examples in shuttle mat'ls
Corrosion examples in shuttle mat'ls
Corrosion examples in shuttle mat'ls
Corrosion examples in shuttle mat'ls
Corrosion examples in shuttle mat'ls Area effect: large cathode & small anode - corrosion accelerated electrochemical cell current density high try to keep potential anodic areas large relative to cathode
Polymers - the nightmare begins I am inclined to think that the development of polymerization is, perhaps, the biggest thing that chemistry has done, where it has the biggest effect on everyday life LORD TODD President of the Royal Society of London
What are polymers? Why important ? Long chain molecules Extraordinary range of physical properties Many (not all) are cheap