chapter 1.2.3.4 review second half Flashcards
chief advantage of lacquers developed during ww1 over varnish oils
left clear film that could be easily pigmented. page4
why is oxygen important to corrosion reaction. what does it cause
with out oxygen the process slows or stops. it is a depolarizer
in any electrochemical reaction which half cell is more negative
the cathode
which side does reduction take place positive or negative
at the cathode
which side does oxidation take place positive or negative
at the anode
how to control mil scale
by pickling or blasting
______ ______ is from mild surface contamination caused by solid particles depositited from the atmosphere or particles that remain after metal has been processed.
cause of filiform corrosion
should salts be removed from metal before coating
yes
3 types of coating exposure from ppnt slides
atmospheric
immersion
underground
earliest known painting made from
naturally occurring oxides
when you need strong adhesion, cohesion, inertness, intercoat bonding, distension
when to use a primer
this provides : resistant seal, intitial barrier to environment, resistnce to chemical, water, and weather, tough surface, pleasing appearance
top coat
first protective coating developed by Egyptians for ships
various pitches and balsam
what coating system did railroad develop for steel riveted bridges.
red lead-linseed oil primer followed by linseed oil-graphite topcoat
where the metal loss takes place
anode
anode, cathode, electrolyte, external contact
four parts of electrochemical corrosion cell
which metal has the greatest tendency to to go into solution
the most negative
what is needed to slow or stop corrosion in a corrosion cell.
a big anode
four parts of coating
binder, vehicle, solvent, pigment
will dissolve the binder, transport the combination to the substrate, and aid in wetting the substrate
solvent
converts a coating into a dense, solid, adherent membrane. it provides a uniformity and coherence.
binder
react with substrate to provide passivated surface, produce color, reinforcement
pigment
binders also known as
vehicles
refers to the amount of water that is picked up and retained within the molecular spaces of the coating
water absorption
the rate at which moisture vapor will transfer through a protective coating when there is a difference in moisture vapor pressure.
moisture vapor transfer rate
the passage of water through a semipermeable membrane from solution of less concentration to one of greater concentration
osmosis
the forcing of water through a semipermeable membrane by an electrical potential
electroenosmosis
resists the passsage of any electrons and thus preventing any metal from going into solution at the anode
dielectric strength
transfer of ions from the exterior of a coating to the substrate
ionic passage
ability of the coating, and the resins from which it is formulated, to resist breakdown by action to chemicals to which it is exposed.
chemical resistance
the corrosion at a break in the coating, growing back underneath the surface of the coating away from the break.
undercutting
solvent evaporation, oxidation, polymerization, inorganic, change of phase, coalescent
film forming mechanisms
Film forming mechanisms
Solvent evaporation. Oxidation. Polymerization
Inorganic. Change of phase. Coalescent
