What's best to use on bare metal??

[hemi-hampton]

If you read the tech sheets you'll notice a NOTE: or small print at bottom saying" Film build of 1.2-1.5 mils of DPLF is Required, or the surface must be treated with metal cleaner/conditioner or coated with DX1791/1792" I think it takes 2 coats to provide 1.2-1.5 mils. So from what the tech sheet is saying, if your only putting 1 coat of DP epoxy on you better (Wash) Etch prime or metal condition. Seems some people have not read this small print?  You would not want to prime over blasted metal that has been blasted with baking soda, walnut shells or any other very fine blasting method. On interior blasted parts I usually sand with 80 grit & definately on exterior. 80 grit sanding on metal is not the same as 80 grit sanding on painted or primed parts. LEON.

[BlueSS454]

Etch primers were used for just that...etching, or biting into previous topcoats or substrates in order to get the new material to stick to the old.  With blasted metal, it's already etched therefore no need for an etch primer.  Etch primers were generally used for refinishing old laquer paint jobs. 

If one reads the PPG tech sheets, etch primer is for bare metal.  Also, the etch is not to be used on media blasted metal.  Can someone explain why?  I don't know, but that's what the tech sheets say.  The DP epoxys can not be used on PPG DPX170, or DPX171 etch primers, but can on DX1791.  Read the sheets of both products you want to use to check compatibility.  I think the etch primers are the easy way out, and the tech sheets say they are for faster throughput, lower inventory, and higher productivity, and the metal conditioners say they are for maximum adhesion and corrosion prevention.  I prefer the PPG DX579 metal cleaner, then DX520 metal conditioner, followed by DPLF epoxy primer.  Here are links to the etch primers:
DPX170/171
DX1791

[hemi-hampton]

As far as I know the etch primer for bare metal only & not old sustrates, Old substrates such as Laquer or any other paint needs to be sanded, Once sanded, this sanding provides the adhesion needed, so no need for a Etch primer. Just my LEON.

[superbirdtom]

Etch primers were used for just that...etching, or biting into previous topcoats or substrates in order to get the new material to stick to the old.  With blasted metal, it's already etched therefore no need for an etch primer.  Etch primers were generally used for refinishing old laquer paint jobs. 

If one reads the PPG tech sheets, etch primer is for bare metal.  Also, the etch is not to be used on media blasted metal.  Can someone explain why?  I don't know, but that's what the tech sheets say.  The DP epoxys can not be used on PPG DPX170, or DPX171 etch primers, but can on DX1791.  Read the sheets of both products you want to use to check compatibility.  I think the etch primers are the easy way out, and the tech sheets say they are for faster throughput, lower inventory, and higher productivity, and the metal conditioners say they are for maximum adhesion and corrosion prevention.  I prefer the PPG DX579 metal cleaner, then DX520 metal conditioner, followed by DPLF epoxy primer.  Here are links to the etch primers:
DPX170/171
DX1791

>>>>>>>>>>>>>>>>>>>>>>>I believe what you are thinking of is adhesion promotors. which have been around for 25  years or so.