Help with coverage issues

Looking at those picture pretty hard and I don't see a lot of evidence of any Iron Phosphate pretreatment. No dull grey matt finish. Should be about 130 mg per sq ft for iron or 300 mg for zinc phosphate.

But to address the question of applying an epoxy/polyester UV resistant powder into the 'cracks and crevasses' of this weldment lets consider the [sp?] Faraday Cage Effect.

Physics tells us the electricity follows the path of least resistance. Reaching into a corner is not the shortest path. The electrostatic charged powder paint is not going to reach the far corner when another surface is nearer. The powder from the gun follows the electricity. The straightest line. Charged powder leaves the powder gun and is attracted to the closest substrate. Not the corner.

Two cures:

1~Turn the power pack 'OFF' and use the powder gun to blow the uncharged powder into the corners. Can be done before the balance of the weldment is p-coated or after the whole weldment is p-coated. What ever gives the thinest mil build.

2~Or p-coat the corners hot with the weldment preheated. Again blowing uncharged powder into the corners and a quick fuse to the weldment's corners. Not the best way to coat the corners.

HINT: Powder is most reactive to the electrostatic charge when large partical virgin or nearly virgin p-coat with minimal reclaim is used. Try to stick the powder into the corners using a virgin powder. With or without the power pac electrostaics turned 'ON' or "OFF'.

Speaking of RECLAIM Powder Booth; Zenon Biendgua, Bill Diaz, and Bart Amota worked very hard on developing a gun designed to address this problem. Their gun mentioned by Dustin Gebhardt is called a TRIBO. I'm not sure but I believe Reclaim was purchased by Wagner.

3~Look at that back draft dry filter liquid booth. She's no powder booth, the substrate ground is near zero with all the paint build up. A clean hard ground to the substrate is necessary for best powder transfer. Paper on the floor catches the overspray?

If I was painting these weldments I'd use a minimum three stage hot spray washer, and after force drying, the weldments would be hung from an overhead track on a spinner. A manual push trolley would fine for now. I don't know if this change is a EPA mandate or just a look~see at powder.

Additionally I see caps protecting the threaded fasteners used to secure the weldment. These might be sold with the unit or just threaded in to protect the welded nut. Air gunning these bolts in and out might be eliminated by 'plugging' the nut then p-coating.

Plugs once loaded up with cured overspray can be cleaned by rolling them 'tween the fingers.

Please let me know if any of this helps. I understand the concept of using what you have and gave my two cents in squeezing the most out of what that may be.

skip.

Last edited by skip (02/01/2010 - 02:50 PM)