Ospho after sandblasting ?

I guess I'm not understanding the need for Ospho if the panel was media blasted. Did the media not remove all the rust? My experience has been that any Ospho residue that gets (got) missed causes adhesion issues (delamination) for epoxy primer. Whereas the abraded surface from media blasting gives a good tooth for the epoxy and doesn't have adhesion issues. I've since eliminated the Ospho step.

In a similar case, a local machine shop did some powder coating for us on some brackets and rather than media blast the part, used a "pre-treatment" solution to rough up the surface of the part. The powder coat delaminated from simply assembling/tightening the hardware. For any powder coating I've been involved in since, the part is always media blasted before it leaves my shop so the powder coater doesn't need the option of the "easy" process. I have experienced ZERO instances of delamination in doing so. Snake oil is snake oil, and shortcuts normally show themselves sooner or later.
 
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MP&C said:
I guess I'm not understanding the need for Ospho if the panel was media blasted. Did the media not remove all the rust? My experience has been that any Ospho residue that gets (got) missed causes adhesion issues (delamination) for epoxy primer. Whereas the abraded surface from media blasting gives a good tooth for the epoxy and doesn't have adhesion issues. I've since eliminated the Ospho step.

In a similar case, a local machine shop did some powder coating for us on some brackets and rather than media blast the part, used a "pre-treatment" solution to rough up the surface of the part. The powder coat delaminated from simply assembling/tightening the hardware. For any powder coating I've been involved in since, the part is always media blasted before it leaves my shop so the powder coater doesn't need the option of the "easy" process. I have experienced ZERO instances of delamination in doing so. Snake oil is snake oil, and shortcuts normally show themselves sooner or later.
Click to expand...
I couldn’t reach all the spots. There’s little nooks and crannies that have this factory rubberized undercoating that I can’t get off for the life of me. I don’t trust that there’s no rust in there so I wanted to run some Ospho in those spots. Definitely wish I didn’t now.
 

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I didn't read all the comments here, but I have developed a method for rust free panels to paint at your own leisure without Ospho. I can give an overview or go into details if still interested
 
Say you've brought panels to bare metal and they're wet for what ever the reason or you want to remove the film. I use pressure washer, Hold 102, distilled or osmosis water, and 1/4 hp pump. Mix Hold 102 & the pure water into say, 5 gal pail. Connect pump (hose) to pressure washer and pump. Submerge into pail. Voila. It isn't good to run either washer or pump for more than a minute without actually spraying.

*some pressure washers can actually draw water as opposed to requiring pressure like a tap
(municipal water)

Hold 102 gives you several days free of flash rust. If you need more time, put panels in a room with dehumidifier set at 40% or less. (if your in a dry part of country, this step not necessary.
 
reallylongnickname said:
Say you've brought panels to bare metal and they're wet for what ever the reason or you want to remove the film. I use pressure washer, Hold 102, distilled or osmosis water, and 1/4 hp pump. Mix Hold 102 & the pure water into say, 5 gal pail. Connect pump (hose) to pressure washer and pump. Submerge into pail. Voila. It isn't good to run either washer or pump for more than a minute without actually spraying.

*some pressure washers can actually draw water as opposed to requiring pressure like a tap
(municipal water)

Hold 102 gives you several days free of flash rust. If you need more time, put panels in a room with dehumidifier set at 40% or less. (if your in a dry part of country, this step not necessary.
Click to expand...
Pressure washer isn't necessary, you can probably do by hand. Also, pump may not be necessary - can use gravity feed by say a rain barrel. It may offer enough pressure for the washer. I haven't explored these options. Just don't use city water. Too much chlorine and minerals.
 
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