Surface preparation - Excessive blasting 1

[vesselrajj]

Dear Experts
I am new to the world of coating inspection. If I do excessive blasting on a surface which already having a profile of 60 micron(for example), what will be the consequences apart from excess abrasive consumption.Plz guide me
Regards
Rajj

 

[tbuelna]

What do you mean by excessive blasting? Did the blasting simply degrade the surface to the point it no longer meets the 60 microinch roughness requirement? Or did it remove enough material so that the surface no longer meets dimensional/tolerance requirements? It would not seem difficult to modify your grit blast process to produce the final surface roughness noted.

 

[CoCoE]

Excess blasting may cause surface defects, or even it can cause polishing of the surface (less surface profile). By the way, why are you doing excess blasting than required?

Cococa

 

[PersonalProfile]

I am not an expert, though assuming: you are referring to substrate preparation, prior to the application of a protective treatment; blast profile could result in coating's defects, including non-conforming DFTs etc.

This may be of interest:

http://www.nace.org/cstm/Education/Program.aspx?id=dcf75ff6-8816-db11-953d-001438c08dca

Regards,
Lyle

 

[tbuelna]

The OP asked specifically about "excessive blasting" and coating inspection. There was no mention of the specific coating process, but many metal coating processes use grit blast for surface preparation, and the grit blasted surface is required to have a maximum roughness. One QA check required in the coating process would be verification of the surface roughness after grit blasting.

 

[Terrytp]

excessive blasting doesn't really have any effect on the blast profile , the important thing to to be aware of is, excessive blasting can reduce the pipe wall thickness , pipe specifications have a '+ or -' tolerance on wall thickness tolerances.

 

[david339933]

Excessive blasting will require more coating to cover the peaks and achieve the desired dft....otherwise you may have spot staining/rusting where the peaks are not adequately coated. You can sand down the peaks somewhat, ensuring a good cleaning prior to coating.

 

[CoCoE]

Dear David339933,

Can you explain how excessive blasting creates high profile?

Excess blasting never means excess profile. Excess blasting may cause slivers, delaminations, or burnishing.

CocoE

 

[david339933]

To say that excessive blasting never means excess profile is not accurate. Depending on the blast media and blast methods used, excessive blasting can increase or decrease surface profile. Excess profile results in additional coating required as stated above, or inadequate profile can reduce adhesion. The blast profile will be the first thing affected, prior to any slivers, delaminations, or burnishing.

 

[CoCoE]

I would stick to my opinion which is based on my experience. Excess blasting does not mean excess profile. If it means so, then making one of the idea to increase profile should be excess blasting. But it is nowhere done.

 

[Tmoose]

blasting thin flat sheet metal can distort it, similar to shot peening.