Stud bolt corrosion

[cpcdesigner]

Being on the gulf coastal, and the bad location of cooling tower systems in our units. My question is, using standard CS A105 flanges with A193 B7 bolting, is it true that bolts in the flanges act as controller of the rusting problem, and will rust before the flanges, but if hot dipped bolting was used for the flanges the flanges would rust out faster than with A193 b7 bolting?

 

[rustbuster1]

There is no basis for suspecting that B7 bolts cathodically protect the CS flanges. I suspect this "folk lore" may arise because the bolts are likely to corrode to failure sooner (because they get thinned all around and break because they are loaded). Galvanizing the bolts will protect them and also protect the flange to some extent. A simpler remedy is to smear a coating of a petrolatum paste like Denso Paste on the flange connection. This prevents corrosion and keeps the bolt threads lubricated for any future disassembly. These paste can be removed easily with mineral spirits.

 

[negotiator]

To CPCdesigner: Ultimately as the hulls are finished and
flange work is past weldment stage, I have crew sprayers
cover any questionable areas with K200 Metal-Etch Epoxy
primer. This nullifies the 'nobler metal factor' NOW.
I went through the books, 'tried this - tried that, but
now a trouble-free element on my oil barges and my mind is on other matters.
thestocksguy@hotmail.com

 

[cpcdesigner]

Thanks guys this helps alot. Negotiator where would I get this K200 Metal-Etch Epoxy. Does this substance need to be reapplied ever so often?

 

[whb]

Even v faced this problem but after sandblasting the problem got solved to 75%.
vj

 

[rustbuster1]

K200/201 is an Acrylic urethane primer surfacer made by PPG.
I have trouble seeing how it works here - it's a common surface smoother for body work on cars. Nevertheless, the notion of finding a convenient protective coating (none more convenieint than paste in my experience) is valid. Perhaps Negotiator could clear up his mis-statements or provide further help, such as a description of the product? I would expect PPG's DTR (stands for "direct to rust&quot mastic primers to be a better choice if one wants to stay with PPG products.