Purpose of a sealer in pre treat

Yes, absolutely, if I understand the process properly.

Sealers are frequently used atop non-chromated conversion coatings to enhance salt spray resistance. They're generally silicate based aqueous solutions that form, on drying, a "glassy" topcoat. Without this, your phosphate coating would be a lot more liable to attack.

Dedalus Environmental - The On-Site Treatment Specialists

Marty-
In reference to your question..."Should we expect to have reduced results if you dropped the sealer and used RO water rinse?"

No. Not if you wanted to run your RO rinse @ 200 degrees F. But in reality, you just cost yourself some more money in energy costs and less money in chemical consumption, probably an even trade or moreso, costing your company more due to inflated energy costs.

You could not achieve a good seal without the increased temperature in your hot water seal....hence, without the hot water final rinse, 1000 hrs of salt spray may not be attained....

Look at it this way....an organic based sealer reacts with the phosphate coating which is somewhat porous in characteristic.....the sealer helps to close this gap or fill in the gaps where needed.......much like a lacquer over a stain, maybe not so much for aesthetics, but for finish and longevity.....or a better way to put it...."it seals the deal"....can you dig it????

later.