HP 80 after hydro

[geoff w]

I took my HP 80 into my LDS for it's VIP, and not surprisingly they discovered a little surface rust inside (I've heard HP tanks are more susceptible to rust), so it needs to go out for a tumble. Since it's due for its first hydro within 6 months, I decided to get everything done all at once

My understanding is that the hydro date is stamped on the tank shoulder after they hydro is done. Do I need to do anything as far as paint or clear coat for where the new hydro date is stamped to keep the outside surface from rusting? If the hydro involves stamping the tank, won't that disturb the surface galvanizing?

 

[redacted]

A "little surface rust" usually only requires tumbling when the shop sees it as an easy way to get a little extra $$$.

 

[DA Aquamaster]

Flash rust is normal. It does not need to be removed until it accumulates to the point where it can start to a) attract/concentrate moisture and b) obscure deeper rusting and pitting underneath.

If a tank is galvanized, the small area exposed by the stamp won't be prone to rust due to the sacrificial action of the galvanization itself. If the tank is painted and not galvanized (Faber, OMS, etc) then a little paint on the stamp will keep it rust free. It's worth noting however that the stamps are placed in the thickest area of the tank intentionally (and are already as deep as any allowable pit in the sidewall) so a little rust is not a serious issue in the stamp on the tank shoulder.

 

[Peter_C]

Most flash rust can also be removed with a simple wire whip in a few minutes. No need to tumble most tanks that only have surface type rust.

 

[geoff w]

On the recommendation of one of the XS Scuba reps at DEMA, I picked up some ZRC Galvanizing Spray (see ZRC - ZRC Galvilite Galvanizing Repair Compound for details). It goes on easy and looks like just the trick for coating where the new hydro date is stamped

 

[XS Scuba]

There have been some good responses to your questions about the hydro process above. On a galvanized cylinder, you should not have any rust issues with the hydro stamp. This is because the hot dip galvanization (HDG) forms a molecular bond with the steel. HDG is not the same as paint, where it is just a superficial layer. Please note, that in rare cases, you may have some minor rusting. This can be removed and sealed using a product like ZRC spray. Also, sometimes the HDG is thick on the crown of the cylinder and some HDG can chip or flake off. This is just excess material and is not a concern for corrosion. Hope this helps.

 

[Dr. Lecter]

Also, sometimes the HDG is thick on the crown of the cylinder and some HDG can chip or flake off. This is just excess material and is not a concern for corrosion.

What about a spot on the side of an X8-130 tank where some baggage monkey smashed it into the deck and thereby caused a dime-sized piece of HDG to flake off? I've already prepped and galv sprayed the area, but hearing for sure that it doesn't matter anyway would be nice.