I want to prepare the samples of coated steel, then we want to test the corrosion resistance of samples in absence and presence of coat. What is the best method to insure the uniform coating layer?
Dear Anees
By simply using a brush & measuring the thickness of the coated layer by an Eddy current method, i.e., Posi Tector 6000 made by Defelsko, Rchmond, ON, Canada.
Dear Anees Abdullah Khadom,
Either you can go with Chemical vapor deposition or plasma spraying
It depends on the nature and composition of the coating. If you're dealing with coatings that can be applied by methods of paint technology, the arbitration method of application is spraying.
I suggest use film applicators if you work with industrial coatings, for example Byk Additives & Instruments or others.
Dear Anees Abdullah Khadom,
You can go through electrodeposition, Either you can go with Chemical vapor deposition
It depends on what type of coating you are using and what kind of corrosion test. Certain corrosion tests you would want to leave the edges uncoated, in others you would want them coated.
For uncoated edges, using a liquid brushable coating, you can shim the perimeter of the metal test panel with plastic shims, say 1" wide x the length of your panel (double sided tape can bond the shim to the metal panel). Measure the shim height to ensure the desired film thickness (add or substract shims as needed), apply the coating to centre of the panel, brush or trowel the coating until its flush with the shims, allow to cure, measure thickness with a DFT gauge after cure.
Electrostatic powder coating by epoxy or polyester is better. Salt spray test (by 5% NaCl solution) shows that it does not suffer blistering and undercutting failure at 500 hours of testing period.
Dear Dr.Anees
Spinning coating is the best method to insure the uniform coating layer for laboratory scale applications , the uniform thickness of the layer due to the spin-off stage and the deposition onto small substrate from a small quantity of coating solution are behind the advantages of this technique over the others like dipping, lowering, spraying, etc. Please remember that the nano oxide materials, if it is in powder form, you got need to disperse into water and/or solvent based colloid like solution.
Best regards
Thank you Mohammed Hussein j. H. Al'Atia for your answer. Is spinning coating by a spinner for Lab scale only? Can this technique be applied in industrial scale? For example, in case of pipe coating
Yes Dr. Anees, spinning coating is industrial scale technique and in the same time the best choice for laboratory scales applications. This process is feasible for any geometry only when the substrate spin around an axis should be perpendicular to the coating area. This condition can not achieve with pipe geometry.
Thanks
Dear Dr. Anees,
I agree with Dr. Mohammed and also, you can a spray deposition method to get a uniform coating film to get a good of corrosion protection.
Regards,
Dear Anees
Beside all the above suggested answers, applications of a brush/ a roller for surface metallic coating could be useful for a heavy organic coating like Epoxy coating, coal tar coating, and so on, for laboratory tests.
Hi Anees
It depends on many factors
1-Analysis that will be done after corrosion test, for example, if it is SEM thickness is not important if it is XPS thickness is an issue (spin or dip).
2- Coating itself, for example, solgel coating you can't increase the thickness (dip or spin) so you will use dip or spin if it is epoxy, you can reach sub cm (brush or spray is ok).
3- Application
Finally, the technique of corrosion testing, EIS or noise thick or thin coating is OK using an even brush if it is polarization you need a thinner coating.
Could you please give more details.
Regards
Gobara
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