2Pac is 2Pac, a bloody awesome paint product that was designed and developed to work on ALL metal surfaces and others. If 2Pac isn't sticking to your engine block then you, (or your contractor), didn't clean it properly. Before I clean a panel for painting, I consider what elements this panel has been exposed to. This helps me determine what cleaning processes are required for the panel, (object). There are only two forms of cleaning when considering paint, they are Mechanical in the first instance and Chemical in the second. Painting always requires BOTH. Mechanical involves sanding etc, chemical is self explanatory.
Your engine block has been exposed to ALL of the nastiest agents out there to kill paint, so you MUST mechanically clean your metal surfaces first with either sandpaper, die-grinder, D.A., Angle Grinder etc, then acid wash your block with a mild degreaser agent then shampoo, YES I SAID SHAMPOO, the block off with a good quality car wash, then dry the block off ENTIRELY. That means DRY.
Now comes the interesting bit, you need to apply a good quality DEOXIDINE solution to the block, this is a metal treatment product and is comprised of Phosphoric Acid. Generally, the mixture as per instructions is 50:1 water to Deoxidine but I always go for no more than 25:1. Deoxidine removes heat and rust scale, other acids and oils and more, refer to this link for more info.
http://www.chemicalcontacts.co.za/acid.htmDeoxidine must be applied in a unique manner and preferably with scotchbrite pads (green). Apply with scothbrite and vigorous rubbing in small areas NOT WHOLE BLOCK AT ONCE. then wash off that area with PLAIN CLEAN WATER, then DRY with Clean Dry Rag and Compressed air. If done correctly, you will notice a blue to yellow tinge to the metal surface. Do this untill the block is done entirely. In other words it is a two step process per area that is treated.
Now that you have completed these steps, you must now protect the metal surface from future contaminates, (i.e oxides), I always use an etch primer in this instance, UNLESS USING A PRODUCT THAT STIPULATES NOT DOING SO. This will result in a metal surface that will remain oxide free and ready for primer/paint in the very NEAR future, days not weeks fella's.
And as always, I expect you shall always use the correct PPE whilst doing the job yeah. This is a definitive and exhaustive explanation on how to clean metal for paint. I can go on but this will suffice for all general AUTOMOTIVE uses only. Spread the word.
Regards,
PanelAndPaint.
