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PostPosted: 12 Dec 2011, 23:57 
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Joined: 15 Oct 2010, 17:50
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Automotive type primers are all high solid primers ... they're designed to be sanded down for a smooth appearance, and they all stick perfectly to themselves. So, you can lay down multiple coats of primer, to build up a workable surface, and sand smooth.

The general rule with automotive type paints is simply use the same brand of paint for your primer and top coat. You also need to pay attention to compatibility but that's usually on the labels.

For flaws that show through the primer, such as a scratch or dimple, use glazing putty (also at your automotive paint store). *Not to be confused with the product of the same name used to install windows*. Glazing putty can be used under any type of paint, however. It comes in a tube and is very fine; not like bondo or other plastic fillers which are usually two-part. Just put a dab on the area you need to fill, let it dry, and sand as normal.

Color choice for automotive paint primers play a role in your topcoat appearance. Grey primer is neutral but light; red primer is dark but will show through light colours.

Black is your contrast primer, which you don't really need to worry about unless you're working on curved surfaces. In automotive use it is a guide coat and is low solids ... ie when you sand or otherwise find low spots and follow with a prime in black, you can sand a second time and if there is a low spot remaining, you will have black showing surrounded by the grey or red, so you know it needs more work.

Black might be useful if you are doing some non-standard enclosure shapes, but generally not important for flat metal enclosures; as a low solid primer it's basically designed to be sanded away but is OK as far as sticking to other primer coats go, so it can be topped with a grey/red primer as your last coat in prep for colour coat.

If you use a basecoat/clearcoat system (doesn't necessarily have to be automotive paint) the clear coat can be applied heavier (multiple coats) and any imperfections in the surface (dust, pinholes, variances in sheen, etc) can be fixed in the clear layer instead of risking thinning or damaging the colour coat. Clear coat can be re-applied many times if necessary.

The spray cans at your local auto parts store work fine for all these steps, and are good metal surface paints. You can also fid suitable paint at your hardware store, but the metal primers are not usually as good (low solids primers).

Also, if you have a specific colour in mind you can go to an automotive paint shop (not your local retailer, generally ... someone who sells paint to auto body shops) and they can make up a spray can with any colour you see on the road in it. That amount of colour should be fine for a DIY chassis, but you might want to consider a proper spray gun and cans of paint if you want to cover speakers, for example, as it would get expensive in spray bombs.

Don't use two-part automotive paints (ones you need to mix with hardener and spray in a defined time) in a DIY project; they are toxic and you need an active fresh air supply type mask, not just particle mask like you find at the hardware store.

People who paint cars "in the driveway" have always watered down the area before painting to hinder dust. It works reasonably well (for dust ... the paint jobs vary).

The Tyvek suits are handy and allow you to wear comfortable clothes; they're inexpensive at home paint stores. Gloves are also a decent idea. Although most spray-can paints are reasonably safe, with caution, people do develop contact dermatitis from things like paint. You could be fine for years but once you get a reaction, you will always get a progressively more serious reaction to contact, so cover yourself and try not to get paint (or epoxy, or whatever) on your skin.

Cleaners like acetone and kerosene can carry toxins through the skin to the underlaying layer. That is why Motor Oil is considered carcinogenic ... clean motor oil is fine but used oil has compounds suspended in it that will be carried with the oil through the skin. No eating, no smoking, no touching the eyes or lips.


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PostPosted: 11 Apr 2014, 01:39 
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Joined: 11 Apr 2014, 01:36
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I think you are making this way harder than it needs to be. Just paint it. Then wet sand and polish any imperfections that turn up. Trying to make an effective, dust-free environment is going to take a lot more time and effort than wet sanding and polishing will.

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