You can you use sinusoidal anodic polarisation to initiate.

In high salt concentration

If use polarization, there are two problems, firts it may have pitting on the outer suface of crevice; second, there are hydrogen bubbles on counter electrode which is not good for my acoustic monitoring. Because my purpose is for online monitoring, the anode and cathode of my crevice sample are not iosolated.

I think the better way to increase the monitoring sensiblity is to incease the contact area,

Generally speaking, you have strictly obeyed the ASTM standard and the results should be reliable. If you would like to accelerate the crevise corrosion, you have to modify parameters or other external cultures, which vary from the standard. But the results are still acceptable. We had carried out crevice corrosion on Alloy 22 in neutral NaCl solution using the same protocol but under various temperatures. The crevice corrosion did accelarate when the temperature was elevated to about 120 degree C. We had same concern when the tests were terminated and we inquired a couple of big guys in corrosion. They replied pretty positively about our results. One of them commented to use a term 'modified standard' to explain our results. Hopefully it is helpful.

I also agree with Chamas answer. Increasing contact area is definitely correct but also highly materials oriented. We used Alloy 22 with contact area more than 100 cm2 in the electrochemical cell but could not observe the crevice corrosion in short time interval.

Temperature is a key parameter in chloride containing media for both crevice initiation and corrosion rate.

Yes, that is what we concerned when we started varying temperature for crevice corrosion.

I do agree with increasing T in order to accelerate crevice corrosion, also if you apply polarisation you can use a big auxiliary electrode which surface area be at least 5 times the area of the sample under crevice test.

In austenitic SS immersed in natural seawater, crevice formed easily with a low anodic polarisation (200 mV of overpotential)

With industrial crevice corrosion, where cooling coils are used with a glycol solution, we saw that the quality of welding was a major cause of its formation. The diluted (25%)glycol solution with water (that had the standard salt content) gets into the weld cracks due to poor penetration, and crevice corrosion starts destroying all the welds on the vessels. Major incident that resulted in destroying a large number of vessels. Corrective action is not possible as glycol leaks out of the coils. .

So how can these factors point to a test procedure? The temperature of the NaCl solution can be increased but the operational temperature in the above case was at -1 degree C.

Is it possible to increase the concentration of the solution (H2O2 and NaCl) and the test period? Can you measure the distance between the two plates?

These factors, time, temperature, distance between the two plates to allow depostion of the salts in the crevice, and concentration will all have an impact on the formation of CC.

In order to accelerate the corrosion efficiency you must know what are the anodic and cathodic reactions which are responsible for your corrosion process. Off course the anodic reaction is metal dissolution, but in your case what is the cathodic reaction. If oxygen reduction at the outer area is responsible for consumption of the electrons , then increasing temperature will activate the anodic reaction but will sow the cathodic reaction due to decrease of oxygen solubility. Adding more oxidizer such as FeCl3 will induce a new cathodic reaction of ferric ions reduction. See the chapter on localized corrosion from Fontana book.

In order to accelerate the corrosion efficiency you must know what are the anodic and cathodic reactions which are responsible for your corrosion process. Off course the anodic reaction is metal dissolution, but in your case what is the cathodic reaction. If oxygen reduction at the outer area is responsible for consumption of the electrons , then increasing temperature will activate the anodic reaction but will slow the cathodic reaction due to decrease of oxygen solubility. Adding more oxidizer such as FeCl3 will induce a new cathodic reaction of ferric ions reduction. See the chapter on localized corrosion from Fontana book.

Thanks very much for everyone.

Actually, the purpose of my project is to monitor crevice corrosion by acoutic emission technique which is very susceptive to acoutic signals caused enviroment change like bubbles from cathode reaction or tempareture increase etc. The frst step is to get the real corrosion signals without interference. Thus, experiment carried out in room tempareture, 35g/L NaCl, and induced by H2O2. The corrosion signals are two weak and few for anlysis in this condition because the corrosion rate is not fast engouh in my opinion. The ideal solution is to find a good way to accelerate corrosion by quiet method.

Any way, the T and FeCl3 worth to try. I have tried to increase T to 60°C, problem is too much envrioment noise.

The low polarization if cant get the hydrogen bubbles on cathode it might work, but I tried polarization before, it was easily creating piiting in the outer surface of sample.

I do agree with Mr.John Cluett, because the monitor need to fit the real industry condition, that means it is really diffcult to get the same severely corrosion like industry plant at lab.without high envrioment noise, in this case, we are in a dilemma: quiet envrioment, slow crevice corrosion but too few information; noisy condition, high corrosion rate but too many information you do not know which are really from corrosion.