Ask the Expert Question-and-Answer Archive

by Ron Joseph

July, 2004

Silica Spots - Abrasive (Sand) Blasting of Steel

Q. After sand blasting with sand there are small 0.1-0.2MM white spots on the surface. I presume that these are Silica spots. The surface will face high tempetature and high condensation in the future. Can these spots cause any blisters or other defects in the future? Thanks in advance for prompt reply.

A. Thank you for your email. It is quite possible that the white spots on the metal surface are from silica. I can tell whether they will cause problems in the future, especially in high concentration environment. One way of checking is to prepare some sample panels and coat them with your standard coating system. After allowing the panels to cure, following your normal curing process, I would suggest that you subject the panels to high humidity under laboratory conditions. You would be looking for blistering and/or delamination .

If this is a large project, then I would definitely want to perform tests before going ahead with the coating system. You do nto want to find that down the road customers reject your product.

If you would like me to perform the tests for you, I will be happy to do so, but on a consulting, fee-basis.

Please do not hesitate to get back to me if you would like additional information.

Best wishes,

Ron Joseph