Right blast abrasive material

[ANS]

Hi,

Just like to know what is the right type of abrasive for surface preparation with requirement of SA 2.5 - SA 3 with angular and sharp profile 65-120 micron. The preparation is for metalizing application and metal finish requires near white metal SSPC-10 or white metal SSPC-5. Thanks in advance for your input.

ANS

[bhellman]

Dear ANS, I think that many of us would like to have some more details concerning your case. First of all, in my opinion SA 3 is the only acceptable cleanliness level.
The surface profile depends on several factors; what is the base material and its hardness, which blasting method is available and to which air pressure (presuming air blasting is used).
Is your question at all including thermal spray? What I can find on the net is that these SSPC norms are directed to preparation of various painting systems, partly as the SA preparation norms are also.
br bhe

[ANS]

The surface preparation is for thermal spray coating (metalizing). It is true that SA standard mostly concern with surface cleanliness which is one of major requiremets for our kind of surface to thermal spray. So, in that sense, we cannot use copper slag to get non-contaminated surface. Most of the people recommand aluminium oxide or steel grit.

For application, we have 2 main scenarios; (1) we blast non-corroded steel (just newly manufactured) and (2) we blast corroded steel (sometimes badly corroded). For material, we blast 2 major types; (a) structure steel A36 (Brinell 150-180) and sheet steel 1020 (Brinell around 120).

And, we use air pruessure (around 120psi) + manual blasting with 600lb pot, #6 nozzle size.

Hope someone can advice/recommand suitable abrasive media (type, mesh size, harndess etc.) for our usage. Any input would be apprecaited

ANS

[Gordon]

Hi ANS

to the Surface Engineering Forum.

Aluminium oxide (brown TiO2 toughened probably best) or angular chilled iron grit. Some where around Grit 20 size (roughly 1 mm dia).

For heavily corroded parts do most of the cleaning with cheaper abrasive grits and then finish off with alumina or chilled iron just before spraying coating.