dk nkf - Nordisk Konservatorforbund Danmark

Figure 4: Tromm III wax crazed and cracked on drying revealing
the metal substrate
the final range was 100 kHz to 30mHz. The data
was collected at the open circuit potential both
times with 10 points/decade and 10 mV amplitude.
A Pt/Nb counter electrode and a saturated calomel
reference electrode were used.
EIS data collection had not been carried out for all
protection systems at the time of writing. Panels
coated with Poligen ES91009 and LPS3 were
tested first because results from the crosshatch test
suggested that they were among those that adhered
best and worst, respectively and that adhesion could
relate to corrosion protection properties. The EIS
spectra taken after 24 hours in solution for the two
coatings are shown in Bode format in figure 5. The
spectra for two uncoated panels are also included
in the figure. Inspection of the impedance at low
frequency gives an indication of the corrosion
resistance of the coating. The highest impedance
value at 1 Hz was for the panel coated in LPS3 (panel
TTG). The two panels coated with Poligen ES91009
(KKG, KKH) had better corrosion resistance than
uncoated steel. Panel KKG appeared corroded and
the coating had lifted off after 24 hours (figure 6).
It can be seen that the EIS spectrum for this panel is
similar to that of uncoated steel.
The entire shape of the spectrum is relevant to the
coating behaviour. The spectrum of an intact, new
coating should be linear. This can be seen in the data
for panel TTG at frequencies above approximately
182
Table 4: Adhesion of surface treatments to Q-panel
surface treatment protection
mechanism
percentage
adhesion to Qpanel
(%)
Corroheat 4010 corrosion inhibitor 97
Tectyl 506 rust
preventative
corrosion inhibitor 100
Ship-2-shore corrosion inhibitor no film formed-not
Industrial
measured
SP400 corrosion inhibitor 95
Rustilo 2000 corrosion inhibitor 100
Rustilo 3000 corrosion inhibitor 100
VpCI-386
acrylicprimer/
topcoat
corrosion inhibitor 100
Tectyl Glashelder/
Klar spray
barrier to water 100
Renaissance wax barrier to water 98
Cosmoloid H80 barrier to water 85
Tromm III barrier to water 99
Paraloid B72 barrier to water 86
Paraloid B72 with
1% perfluorodecyl
iodide
barrier to water 95
Dinitrol Car/4941 barrier to water 100
LPS3 barrier to water 40
Poligen ES91009 barrier to oxygen 100
Frigilene barrier to oxygen 100
Incralac barrier to oxygen 90
10 Hz. The flatter shape of that curve at lower
frequencies indicates some reduction in corrosion
protection. By contrast the curves for panel KKG
and uncoated panels are linear only at the highest
frequencies and flatten quickly.
Conclusion
It is clear from the number of literature references
found in the planning stage of this project that
protection of iron and steel surfaces is a highly
active area of research both in the conservation and
commercial fields. However, selection of a suitable
product from literature sources alone is a minefield.
The three key factors which prevent inter-research
comparison are variation in dry film thickness, use
of non-standard evaluation techniques and selection
of appropriate reference coatings. The experimental
design of this project aimed to reduce the number of