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Swedish Standard St2 / St3

Q. Good morning sir, can you kindly tell me what's the meaning of Sa. 2.5 & St 2.5 standard? For building works, how can we use sand blasting.

wing tat kwok
technical director - china hong kong
May 1, 2022

A. Hi Wing. Sa 2.5 is a surface finishing standard for sand blasting. Apparently the standards range from Sa 1 (roughest) to Sa 3 (smoothest), with Sa 2.5 being a bit shy of Sa 3. Thread 12526 goes into a lot of detail about these sand blasting standards.

The St standards are apparently for cleaning up surfaces with hand or power tools rather than blasting. There is an St 2 standard and an St 3 standard, but I am not sure that St 2.5 even exists -- there may be a quantum jump from Sa 2 to Sa 3; please see

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey
May 2022

⇩ Related postings, oldest first ⇩

Please advise what Swedish Standard St2, St 2 1/2 and St 3 mean in finishing surface. Our company is involved in some corrosion protection work here in Taiwan. Recently, we have search for some products which require a surface finishing standard in accordance with St 2 or 2.5. We like to know more about the standard and related information. Please be kindly to advise. Look forward to hearing from you. Regards, Many thanks.

Viktor Yue
Painter - Taiwan

These are specific ratings of surface finish/cleanliness within standard SIS 055900, which is apparently now ISO 8501. Suppliers of paint testing instruments can sell you binders which include the standard and examples of such finishes, or you can obtain the standard from ISO. It's pricey.

Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

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