How am I treating rust and paint choices.
Today I using a process to treat rust. It may change in the future but this is the present procedure.
1. assessment, if it's weak, through or you can not access it, you need to cut. I find weld through primers are weak and don't last. The white iron phosphate, black phosphate or black oxide created chemically is better rust prevention and does not seem to add porosity to welds.
Small parts that fit in a 5 gallon bucket get wire wheeled and an overnight soak in 50% vinegar 50% water bath and hosed off. I am considering a 55 gallon drum to do this in the future but haven't found a part that needs this that i am willing to tackle. Control arms, i have my eye on you...
2. Bring the rust and paint down to the point you can chemically treat the area and you are sure none is hiding under paint. Wire wheel, wire knotted cup brush, Flap disc, roloc discs. Occasionally carbide shanks and cone sanding shanks.
3. Choose your chemical weapon. I like phosphoric acid in liquid and gel form naval jelly which has sulfuric acid as well. While treating I agitate with a steel bristle brush. If it's brown do it again until it's black or gray.
4. The rinse, you need to rinse while wet. If it has dried you need to re-apply your acid and revive the surface. I like to skip the water and go for acetone and brake clean.
5. Check color after and make sure you see no browns or reds.
6. I have left the phosphoric acid liquid to dry unpainted for 6 months and not seen changes or rust. I have also removed the liquid while wet with acetone and had it flash in a week. So you need to paint pretty fast or work in small sections. You can also re-wet and remove at a later date. If its a long project i want to watch my surfaces before putting them through finishing so you know the base material is stable.
PAINTING
I am not a painter, but here are some of the self discoveries i have made:
7. I find I like using primer sealer between different paints. A lighter grey primer shows any rust coming through if you need to leave a part in primer for a while. It just happened recently with the door hinge mount plates, I saw a speck of rust in the bottom of a pit come through the paint and retreated them.
8. Grit or "surface key", 400 grit before primer 600 grit before base color seems to leave a satisfactory finish at least for the hack jobs i have done. If its fresh primer i give it a light scuff with a red scotch to knock off any debris and then air gun and tack cloth. If its fully dry high build primer i block with 400 and then 600 for base.
9. Clear, if the part has a ton of curves i will go overboard with clear, so i don't rub through while wet sanding. If its flat or has 1 or 2 bends I usually start with 3 passes of clear and I spray out onto a test panel so i can touch it and decide if its ready for the next pass.
10. wet sanding clear, I like 1000 grit to knock down peel and powder. 1500 grit cross hatched 3 ways for buffing. Make sure you have a good quality sand paper like 3M, with a good car wash detergent in the water. Finish 1st brand didn't take the water well and balled up on me causing me to redo a clear once. I also left the paper for 30 minutes to soak and then over night and saw no difference with the higher grade sand papers.
11. Cut and Polish, I like Maguires diamond cut paste and then Maguires liquid polish.
A note on the use of por15. I have read some like it, some don't. I have seen it fail and seen it succeed. As a rule, I do not paint over any active rust regardless of the name. Either rust is mechanically removed or chemically changed. There are some situations you shot and pray with the chemicals, because you would have to go so deep into disassembly or dissection it's not worth it. I do like por15 on top of other paints with a good key in them, so as a top coat to a primer or a rust inhibitor. Every time i have encountered that when removing paint, it is the hardest to remove aka "great adhesion." I know no manufacturers want other brands under their paint, but this is not going down to bare metal because of budget. .It's the whole encapsulation thing that i just try to avoid in general. Honestly if other products became available locally to me or on amazon i would probably try them after a little research.
As for base color spraying, I have gravity and suction types of air brush equipment i am dying to try on a part. I am currently reading up on paints, thinners and solvents in anticipation. Id love to try this because i only have a tiny compressor and don't have enough cfm for a hvlp gun.
1. assessment, if it's weak, through or you can not access it, you need to cut. I find weld through primers are weak and don't last. The white iron phosphate, black phosphate or black oxide created chemically is better rust prevention and does not seem to add porosity to welds.
Small parts that fit in a 5 gallon bucket get wire wheeled and an overnight soak in 50% vinegar 50% water bath and hosed off. I am considering a 55 gallon drum to do this in the future but haven't found a part that needs this that i am willing to tackle. Control arms, i have my eye on you...
2. Bring the rust and paint down to the point you can chemically treat the area and you are sure none is hiding under paint. Wire wheel, wire knotted cup brush, Flap disc, roloc discs. Occasionally carbide shanks and cone sanding shanks.
3. Choose your chemical weapon. I like phosphoric acid in liquid and gel form naval jelly which has sulfuric acid as well. While treating I agitate with a steel bristle brush. If it's brown do it again until it's black or gray.
4. The rinse, you need to rinse while wet. If it has dried you need to re-apply your acid and revive the surface. I like to skip the water and go for acetone and brake clean.
5. Check color after and make sure you see no browns or reds.
6. I have left the phosphoric acid liquid to dry unpainted for 6 months and not seen changes or rust. I have also removed the liquid while wet with acetone and had it flash in a week. So you need to paint pretty fast or work in small sections. You can also re-wet and remove at a later date. If its a long project i want to watch my surfaces before putting them through finishing so you know the base material is stable.
PAINTING
I am not a painter, but here are some of the self discoveries i have made:
7. I find I like using primer sealer between different paints. A lighter grey primer shows any rust coming through if you need to leave a part in primer for a while. It just happened recently with the door hinge mount plates, I saw a speck of rust in the bottom of a pit come through the paint and retreated them.
8. Grit or "surface key", 400 grit before primer 600 grit before base color seems to leave a satisfactory finish at least for the hack jobs i have done. If its fresh primer i give it a light scuff with a red scotch to knock off any debris and then air gun and tack cloth. If its fully dry high build primer i block with 400 and then 600 for base.
9. Clear, if the part has a ton of curves i will go overboard with clear, so i don't rub through while wet sanding. If its flat or has 1 or 2 bends I usually start with 3 passes of clear and I spray out onto a test panel so i can touch it and decide if its ready for the next pass.
10. wet sanding clear, I like 1000 grit to knock down peel and powder. 1500 grit cross hatched 3 ways for buffing. Make sure you have a good quality sand paper like 3M, with a good car wash detergent in the water. Finish 1st brand didn't take the water well and balled up on me causing me to redo a clear once. I also left the paper for 30 minutes to soak and then over night and saw no difference with the higher grade sand papers.
11. Cut and Polish, I like Maguires diamond cut paste and then Maguires liquid polish.
A note on the use of por15. I have read some like it, some don't. I have seen it fail and seen it succeed. As a rule, I do not paint over any active rust regardless of the name. Either rust is mechanically removed or chemically changed. There are some situations you shot and pray with the chemicals, because you would have to go so deep into disassembly or dissection it's not worth it. I do like por15 on top of other paints with a good key in them, so as a top coat to a primer or a rust inhibitor. Every time i have encountered that when removing paint, it is the hardest to remove aka "great adhesion." I know no manufacturers want other brands under their paint, but this is not going down to bare metal because of budget. .It's the whole encapsulation thing that i just try to avoid in general. Honestly if other products became available locally to me or on amazon i would probably try them after a little research.
As for base color spraying, I have gravity and suction types of air brush equipment i am dying to try on a part. I am currently reading up on paints, thinners and solvents in anticipation. Id love to try this because i only have a tiny compressor and don't have enough cfm for a hvlp gun.
