Greetings,
I planned to make a simple procedure of corrosion testing using an organic coating applied using a brush on stainless steel coupons. But, I still want to follow the standard thickness of coating.
I try to find the standard thickness in ASTM but it is quite hard since almost all astm are quite expensive.
Organic coatings are widely used to ptotect metallic corrosion. The three most important factors to consider for organic coatings are Surface preparation, Selection of primer and Selection of top coats. If the first two factors are wrong the system will fail. The coating thickness must be such that no bare metal is exposed. Multiple coats are needed to cover all pinholes.
While going for corrosion studies,it is necessary to prepare uniform coating with out any exposed areas, as it may results in aggrevation of corrosion due to potential difference. So make sure your coatings are free from voids.moreover there is no particular coating thickness, it's based on materials you have selected such as primer binder. And lastly if the coating thickness increases the binding property decreases in certain studies. So it will be better to have coating thickness in micron regime.
Hi,
Based on application, you might choose from a wide range. I suggest you to search for organic coatings datasheet for a specific application ( e.g. pipeline internal coating, ...). These may give you insight through thickness and effect of coating properties. However if you are going to conduct electerochemical testing, you may have some difficulties at higher thicknesses. For novel compositions, need for some initial optimizations before original testing is routine.
Best of luck
Reza
ِDear Mohamad;
You need a coating with optimum thickness. The coating with low thickness leads to non-uniform film with bare regions. Also, thick organic coatings are difficult to analyse with electrochemical apparatus. So, I suggest you to take into account these considerations (based on my experience, not based on standards!):
1. For more resistive coatings such as epoxy coatings, 100 micron is a good thickness for electrochemical analyses (i. e. EIS measurements).
2. For less resistive coatings with more electrolyte diffusion such as alkyd coatings, 200 micron is a good thickness for electrochemical analyses (i. e. EIS measurements).
The proper thickness depends on the type of coating, and percentage of product solids to form a film with the least number of pin holes. Usually a film thickness of 4 to 8 mils (100 a 200 micrones) is recommended in coatings exposed to the atmosphere and up to 16 mils ( 400 micrones) for high thickness coatings for use in submerged or buried structures.
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