Painting on chromed parts? AAAARRGHHH, I need help

How about using sand/shot blasting to give it a key, then painting?

I did sand it down to give it a key and I used por15 metal ready which is a aqueous solution of phosphoric acid to etch the metal.

As the sanding did not go through the chrome, just keyed the surface, the metal ready is still trying to act on the chrome. This is what I think it cannot do so it failed.

I will take it to work and shotblast it but primarily to get the crud off that is now on it. I sanded the straight parts with my orbital sander and a 180/120 grit which took all the shine of the chrome.

I think I must get rid of all the chrome before I have any chance of success but how without paying heaps to some electro plater who can strip it off?

Whenever I have had to paint a chrome part I have always done the following;

Sanding with 100 grit, then again with 180 grit.

Throughly clean the surface with a clean cloth and paint thinner, then with tack cloth.

Primer coat is done with a self etching primer, see http://www.duplicolor.com/products/primer.html

Wet sand with 220 or finer grit and repeat, I normally only do two primer coats.

How this helps, it works for me.

Do you sand through the chrome?

No not as a practice, just rough up the whole surface.

You are essentially removing the chrome as you rough it up, it is the nickel that you are having trouble with. You might try etching with nitric acid solution 1:1 with water at 120°F....

www.newton.dep.anl.gov/askasci/chem03/chem03370.htm

enjoy

Find a place that re-chromes bumpers in your area and take it to them. They will usually strip it for you pretty cheap. They have tanks set-up for it already. Then all you have to do is give it a light sanding and you are ready to prime and paint.

CK

The advice to find a bumper refinishing shop sounds good - if you can find one that works with chrome in these days of plastic matching bumpers.

Platers in the Cambridge area include K.L.Giddings, and Cambridge Electro Plating. It may be that you know of them already and they are too pricey - but you might get some good advice just by talking to them (at least they will know what questions to ask).

Failing that, it depends on what are you wish to do to the surface after you have treated it. The basic problem with chrome is that is that not much sticks to its oxide - and a thin uniform layer forms very rapidly. Nickel has similar issues, but not nearly so severe and the oxide is easier both to bond to and to remove.
If you want to plate successfully over cleaned chrome, you will need to change directly from oxide etch to plating. If you wish to paint, a suitable etching primer should allow this.

For a more specific answer, see if you can waylay a metallurgist (e.g. from the Welding Institute?) at an astronomical meeting.

Hello case491,

try a seriously good paint stripper called 'Nitramors'. It is pretty cheap and certainly worth trying. Am not sure of the 'active' agent. But, it certainly works on paint and varnish brilliantly!

jfmfit

'Nitromors' – it's available in both 1 litre and 5 litre tins so best to consider just how much paint you need removing, on the back of the tin it advises you the area one litre can cover – so you should get a rough idea how many tins you need to buy. Whilst you're in the DIY store you may as well pick up some rubber gloves, as well as a set of safety goggles too, yes you may look like a prat wearing all of this gear but safety is very important when using this stuff.

Now, before you start to use Nitromors it's very important that you read the safety instructions on the back of the tin. Nitromors should be used in a well ventilated area as the fumes could become quiet overpowering if used in a confined space – this is why it also advices not to use this substance in places such as basements or under stairs.

Next it's time to put those rubber gloves on because the paint stripper is very corrosive (obviously) and it can burn your skin should it come into contact with you (as I found last night, because I forgot to use gloves!). So, you've got your gloves and goggles on (to protect your eyes from falling paint) – what now? First up you'll need to find a suitable container to put the Nitromors in, I used an old tin pan that we neve
r use – you'll also need some clean brushes to apply the stripper with.

Nitromors needs two applications to make it work – you basically apply it the same as you would if you were painting the wood. Using your brush you cover the wood with a fine layer – not too thick then leave the wood for five minutes.

During these five minutes you may notice the paint begins to blister a little (similar to the effects of a heat gun). Once the five minutes are up you need to apply another coating of Nitromors to the same area, this time working the liquid more into the blisters themselves. Once you've treated the area you need to leave it for twenty minutes this time – this obviously gives you an ideal opportunity to make a cup of tea!

During this twenty minute wait the chemicals in the Nitromors really get to work in attacking the paint, on the label it claims that Nitromors can penetrate up to fifteen layers of paint and I can certainly believe them. Once the twenty minutes is up, you then use a paint scraper (I'd recommend a tool called a 'shaving hook' for getting into the nooks and cranny's, basically it's a sharp triangle that you use to get into little crevices and getting paint out of hard to reach places. The Nitromors makes the paint just peel away very easily indeed, exposing the natural wood that has been hiding underneath dozens of coats of paint for all those years.
Using this stuff could obviously be a bit messy, but if you put down some newspaper first for the paint to land on then you should be okay – plus the non-drip formula of the liquid stripper means that it should be easy enough for you to handle.

You aren't the first to suffer - some of the references here may be of interest.

BTW, you can blast chrome with corundum or with water, but its hardness means that silica sand is relatively slow.

Thanks to guest for this link, and to all for all there help.

Certainly the link in the above post is very useful. I have decided that I can actually sand, grind, grit through the chrome sufficiently to try the painting again.

Problem with the etching primer is that I cannot find any that are heat resistant enough, I forgot to mention it is an exhaust system sorry.

I am confident that now I have rubbed my fingers to the bone and I am almost completely through the chrome in most places, it will work satisfactorily.

Many thanks to all.

Regards.

That is a perfect site, many thanks for that.

Do you think you could get away with 12V from a charger rather than killing your battery?

I have actually roughed the chrome up something rotten now with P100 abrasive paper and it has been sprayed one layer. Second layer tomorrow diner time and in the oven for baking. Ready for night time to put on the bike.

If it does not work this way, I will definitely strip the chrome the way it says on that page.

Many thanks.

So are we going to be treated to photos of your new (bright red??) shiny pipes ?

I can't see any problem with using a charger instead of a battery - as long as it's got decent isolation. Don't want to go dipping anything that could end up 'hot' in buckets of electrolyte.

No they are light absorbing matt black velvet.

Here is a picture of them on a dark background.

As said, I have done it now and I am waiting for the second coat but it seems to be a lot better this time than it did first attempt.

With the first try it almost just fell off when I shook the damn pipes.

So, you're building a Stealth bike?

They look just like this picture of my fenders. They are flat white, on a snow covered driveway.

Do you see the resemblance?

I would use aluminum oxide as media for blasting. Do a kind of brush blast: what we call an SSPC-SP-7 just enough to remove the shiny chrome and get a kind of dull finish. Get a profile of 1 to 1,5 mils max.

Prime with an epoxy polyamide 100% solids such as Rustbond at a dry film thickness of 1 to 2 mils. The Rustbond stick to almost any surface and will act as tie coat and will adhesion between the substrate and the topcoat.

Topcoat with a good 2K polyurethane for UV resistance (an acrylic or polyester type) such as Carbothane 134HG or similar.

There's other method but this is an easy one and it works!