Coating under enamel on cast iron tub

[rayge]

The white enamel on my old cast iron tub was peeling and flaking so I removed it with citrustrip. Underneath that enamel the cast iron tub is sort of a slate blue/gray. I might eventually try to put on a 2 part epoxy enamel but right now I would like to use the tub as is. However there is some sort of gray/white coating over much of the tub I would like to remove. Where there isn't this coating the tub itself is shiny and I sort of like the color.

I've tried mineral spirits, paint stripper, acetone and 60 grit sandpaper with no luck so far. I imagine this coat was put on originally so the baked on enamel would bond better to the iron.

Any suggestions on how to remove this coating? I was thinking of using muriatic acid in small areas and then neutralizing with baking soda before rinsing down the drain.

 

[hj]

THERE IS NO "coating" UNDER THE "enamel", (and it is a glaze not enamel on a cast iron tub), unless you have an enameled steel tub. rather than a cast iron one.

 

[Sponsor]

 

[Terry]

The white enamel on my old cast iron tub was peeling and flaking.

It sounds like you have a cast tub that has been painted over. The actual coating on a cast tub is permanent and can only be chipped off.

 

[rayge]

I guess I'm using the wrong terminology. It's confusing.
https://homeguides.sfgate.com/steel-vs-cast-iron-bathtubs-95586.html
https://homeguides.sfgate.com/paint-bathtub-enamel-paint-32879.html
I took pics of the tub wet and then dry where you can see the residue. Timer magnet sticks so it's metal, maybe steel. There was one thick white coat of paint that several applications of citrustrip removed and a single coat of Smart Strip removed in other sections.
I didn't remove the paint from the front face of the tub. It has sliding shower doors.
If that blue/gray coating is permanent and can only be chipped off, can I be more aggressive and use an electric sander to try to remove the residue?
I've also tried goof off, turpentine, sodium percarbonate (oxiclean), hydrogen peroxide, baking soda, CLR, all with with no luck.
I have a respirator because I was trying Kwik-Strip which was useless both as a paint remover and on the residue. I suppose I could try to track down some methylene chloride and try that a section at a time then neutralize with baking soda.
I won't call the residue adhesive because it's not sticky but I figure whatever that white stuff is on there was to help paint ahere. Tub may be American Standard. The bath fixtures are. Likely original to this 60's ranch house.
Once I caulk it I'll use as is, residue or not. Before I sell the house may try something like this
https://www.amazon.com/Ekopel-Bathtub-Refinishing-Kit-Reglazing/dp/B07MCW3KJB

 

[Terry]

Is that American Standard 144 New Orleans Blue?

Sometimes the best bet is to hire someone that refinishes tubs. I seen how they look afterwards, but have never done it.

 

[Reach4]

You are looking at the original color, and I suspect you peeled off the attempts of the previous homeowner to get the house ready to sell.

I won't call the residue adhesive because it's not sticky but I figure whatever that white stuff is on there was to help paint ahere.

When you wet the white area, does it look better?

Try some auto wax or polish. I am not a pro.

 

[rayge]

Oh, I hadn't thought of that. American Standard actually sold tubs in this color then. It looks great to me, but maybe a previous owner had it done over in white at some point. When it is wet, that semi-white pasty looking coating practically disappears, but as it dries the haze is apparent. It's like it was brushed on because it is not uniformly coating the entire tub. I dunno about auto wax however, wouldn't that just be a soap scum magnet?

 

[Reach4]

I dunno about auto wax however, wouldn't that just be a soap scum magnet?

Maybe more like a soap scum repellent.

Consider small dabs for a test. Maybe NuFinish or classic carnauba paste wax. Also Rain-X

Got a friend who polishes his car?

 

[rayge]

OK, I will report back. I have various car waxes but not those.
I did get several quotes for refinishing and they started at $800. Not much competition around these parts.

 

[rayge]

I just ordered this for about $8, and will attempt it before the wax
https://www.amazon.com/gp/product/B008RA5JEW
Arrives in 2 days and will spray a section (with ventilation mask, gloves) and see what happens.

 

[Jadnashua]

I would try buffing it with a polishing compound and a buffing wheel. The compounds come in various grits. I'd probably start with a polishing compound, and if that didn't do what you wanted, maybe go to a rubbing compound (coarser), then followed up with the polishing compound. Usually, that glaze is fairly thick...thicker than a coat of paint. Essentially, it's glass.

Tubs are often already slippery...I'm not so sure I'd want to put some wax in it! To get paint to stick, they may have used an acid to etch the surface so there was some 'bite' for the paint to adhere. That slightly rough surface would tend to hold a bit of that paint, making it harder to get a nice, shiney, surface. Buffing it smooth should restore it.

 

[rayge]

I have some old polishing compound I used for the car. I'll have to purchase a buffer wheel attachment for my drill, or I could just try a small area by hand. I also have rubbing compound. As I mentioned above I tried 60 grit sandpaper by hand to no avail, and I think that would be more aggressive than polishing or rubbing compound.
I tried the methylene chloride I ordered a few days ago - link above. It's a spray but is full strength, only additional ingredient is a propellent. I left it on 20 minutes and then used a teflon scrubber. No dice. I sprayed again so it pooled up and left on an hour, and the residue just laughed.
If I am down to the original tub and if the color is dyed throughout the metal I wonder if heating an area with a propane torch might help lift it off. I have a homeowners little torch.
Waxing might very well hide it. I can try as a last resort but I'd prefer to remove the stuff. Also concerned about slipping on a waxy surface in the shower.
I wonder if there is a bathtub refinishers forum? I'd like to find out what is this tenacious bond.

 

[Reach4]

I suspect you are mistaken in seeing this as a whitish coating rather than the blue finish being frosted.

 

[rayge]

It does appear frosted but it almost appears brushed on. There are a few areas that have no coating. Most of the tub is coated, many areas coated more heavily than others. Those are the areas I attempted to remove so I could get to the shiny surface below.

 

[Jadnashua]

Etching the surface will cause it to dull, and refract some of the light. You need a polishing compound designed to work on a hard, glass like surface. Typical rubbing compounds used on car finishes probably won't cut it (pun intended). You need something that can polish glass. WHen polishing something like this, it will take a number of various grits to eventually bring the surface up to a high polish. Some of the refinishing companies are better than others, but none of them are as hard as a glaze used on the tub when manufactured. There are places that can remove the existing glaze and apply new that is as durable, but that requires removing the tub. In most cases, it's then cheaper to just replace it. They essentially sand blast off the original surface, apply a glaze coat, then fire it in a furnace. Involved and expensive.