MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Dangers of baking soda blasting?

Guys just had an interesting talk to a professional restorer here in Brisbane Australia about stripping with baking soda . He said whilst it is less abrasive than grit the downside is if you use it and then clean down with water you get a highly reactive solution that can corrode some metals, especially any wiring or connections (if you don't fully remove this type of material before blasting and flushing). They still use sand/grit blasting for this reason. Any chemists out there care to comment?
regards
Mark
Mark Mathiesen

Related to but slightly apart from this post.

Has anybody in Aus used/made/adapted a small sand blsting gun to use Soda?

The sort of gun in question is the sort normally sold at car parts shops , with a removable bottom cannister and it "sucks" up the sand from the bottom of the cannister.
M THOMPSON

Try Harbor Freight. A fair balance of inexpensive, intermediate quality occasional use for most items.
Russ
Russ Carnes

Adding water to baking soda will not produce a reactive solution. If anything, flushing a baking soda solution with more water should decrease its alkalinity. It's my understanding that the soda blasting process is water and soda to begin with, so flushing it down with water shouldn't make it any more reactive than it already it. Perhaps the act of flushing can wash it into places you didn't intend it to go. FYI, When you add vinegar to baking soda one by-product of the reaction is H20. Baking soda is an alkaline, so it is slightly reactive to certain types of metal. When in contact with aluminum it will eat away the protective oxidized layer. Copper is a soft metal also so it could damage it as well. You can use it to polish stainless steel but it will never damage it. It's slightly reactive to iron. You can use a baking soda paste to remove rust (don't know how well it works- never tried it). You can also polish silver with it.

So, I don't know if the restorer has a personal experience with damaging metals or if it is some kind of urban legend. I don't think I'd want my aluminum doors and bonnet soda blasted, or pot metal pieces for that matter, but I can't see the process being any worse for your car's metal than an acid dip which people still use.
Mark J Michalak

I had my car blasted with plastic pellets. It worked well as long as the operator is carefull of the aluminum surfaces.

Ed Bell


This is an article that I have found regarding your concern about electrical connectors and the corrosion you mentioned.

In short: The baking soda is hydrophylic. If left alone, it will absorb any moisture from the air and that moisture will cause corrosion. The soda residue must be removed in order for paint to adhere. It seems that washing is a required cleanup step in the soda blasting process. They recommend a chemical added to the pressure washer that prevents flash rust for a few days.


http://www.chesapeakesodaclean.com/media/PDF/CSC-SodaBlast_Auto-Paint-Strip.pdf
Chuck Schaefer

As coincidence would have it, I had my MKI Sprite soda blasted yesterday afternoon. The finished product is absolutely incredible. Providing the metal hadn't been messed with earlier, it looks as if it just came out of the press 50 years ago. The car is bare metal now. Every crack and crevice is clean. Layers of undercoating gone. It's amazing. Anyway, the car can stay as blasted for a long time assuming it doesn't get wet. I was told once welding is done and I'm ready to prime, to wash the car with hot water and washing up liquid. Once dry, if any white residue is present, wash again. Then prime within a few days. I was told it may start rusting slightly, but prepping for paint will wipe it away. The soda pH is about 8.3. I've read adding a little vinegar to the wash will help. I would imagine that electrical connections would not do well if the soda was not neutralized.
Kemper

I had my '61 MGA doors Hood and trunk soda blasted by Connecticut Soda blasting in the US " because it was the safe new alternative " Well the idiot that did it warped every aluminum panel I gave him!!!!!!!!!!!!!!!!!!!!!!!!!!!!. Like all media blasting it all depends on the operator , the correct angle must be used, anything close to 90 degrees will create too much heat and warp the aluminum. After this I had the rest of the car and replacement doors hoods and trunk chemical striped and they came out perfect
Chris Velardi

Soda Schmoda. Can someone tell me the difference between using sharp sand at a low pressure or long distance and softer soda at higher pressures / shorter distance ? The end result is you have to be severe enough to remove the paint and crud, and not overdo it whichever media you chose. Sand is cheaper. My 2c worth.
Art Pearse

You need to use a lower pressure on aluminum; around 60 psi. Steel is blasted at 130 psi.

Sand etc. scourers the surface of whatever it contacts. Soda apparently explodes on contact and lifts off paint, dirt, and debris. It doesn't remove rust staining, but will remove the scale. You can soda blast over chrome, rubber, and glass and it will not cause damage. The rack was left in my Sprite and I watched the guy directly blast the rubber boots repeatedly and they are fine. One of the doors on my car looks brand new with shiny metal underneath. It has to be seen to believed.
Kemper

This thread was discussed between 24/05/2010 and 02/06/2010

MG MGA index

This thread is from the archives. Join the live MG MGA BBS now