Question

We have had a couple of issues lately with 430 steel used for legs and undershelves being contaminated on sites.  We have tested independently and the only result back is saying that the item is contaminated but not specific.  We have been down the route of checking what the items are being cleaned with and that is all fine.  They are separates sites and on some sites we have old 430 tables next to new 430 tables the old ones are fine and the new ones are showing the contamination.  It is baffling, please could you ask members if anyone is having any similar issues.

We have also spoken to our fabrication company and they cannot answer this either.  Any assistance or similar issues appreciated.

Replies

1. Two separate sites with the same problem with the same fabricator supplying both? I had a similar issue of contamination being caused by the fabricator grinding in the vicinity of 430g  sheets in their workshop thus covering it with mild steel particles without knowing. I’d be looking at the fabricator or at least asking them to explain how it’s possible.
2. When they say “contaminated” what do they mean, as I had a customer a year ago that had small rust spots appearing over the surface and undershelves of tabling in the kitchen. The kitchen was not used regularly as it was a small function area.I was advised that these were caused by using bleach products for cleaning..
3. We have experienced a similar problem on a site last year, we found that the steel had reacted with a sealing agent put on the tiles on the kitchen floor, could be worth checking if the floor has been replaced/sealed recently?
4. I have spoken to Williams Refrigeration about a similar issue with some of their new cabinets – the adhesive used on the laser wrapping is a different grade and subsequently if not cleaned off on first use it created what looked a lot like rust all over that wouldn’t come off with normal cleaning, was actually dirt mixed with adhesive in the grain of the steel. Sounded like a bad excuse but in fairness it did turn out to be the case and it very much looked like rust, I’ve seen the same thing on fab from CED where 430 is being used.
5. Yes, we had a similar problem in the last year with wall shelves at a pizza restaurant. They were reported by our client as ‘rusting’ – basically rust coloured discolouration and slight pitting.We queries the sheet quality but the fabricator concerned said they’d had no issues with 430 and ours was a one-off. The client (well known to us) swore that he and his staff were not cleaning down with bleach and were also not placing wet iron trays on the shelves. The ‘staining’ was also appearing on the underside of the shelves. In the end the fabricators did replace the shelves – this was about 6 weeks ago and we’ve heard nothing further, which tends to make us doubt the assurances about the raw material!
6. I have had this issue where the site has used a high acid floor cleaner with no overnight ventilation, older tables can have a thin coat of ingrained  oil after years of kitchen use, the legs rarely get cleaned so they get a small level of protection.
   It doesn’t have to be direct contact with the steel to cause the problem, it’s worth checking to see if the contamination is worse at the bottom, getting less higher up.
7. With 430 steel the parameters for the ferrous content can vary from supplier to supplier i.e. 430 stainless steel from overseas may well have more ferrous than stainless steel manufactured in the UK. I cant remember percentages but suspect the problem is connected.
8. We had a situation once. All grades are certified so not likely it not what it supposed to be. In our case we eventually realised the  fabricator was grinding other metals close to were the tables were being made and this contaminated the stainless. The only way this was cured was to completely re polish the stainless with an industrial polisher.
9. A photo of the problem might be helpful as it would possibly confirm if the problem is due to Electrolytic action by dissimilar metals. This could show itself as a “blueing” effect, pitting would certainly indicate the presence of some form of stronger acid or sodium chloride (salt) solution.
   If some of the table legs are in a moist area then that might be the reason for the differing effects.
   If the legs have been independently tested then I would have expected the metallurgist to have explained the possibilities. As always I would be pleased to talk it through with the member but it is a long time ago since I took my exams in Metallurgy.
10. We have always used 430 for our frames/undershelves without a problem. The only similar experience I had was a few years ago when a client was complaining that the stainless steel fabrications we had installed were ‘rusting’. We too had used the same fabrication supplier for years without any problems, so though it was a little strange. It turned out that they were not properly rinsing off the cleaning products (detergents and/or bleach) during normal washing down and the problem was being caused by the residual product left on the surface of the stainless. This was resolved by cleaning the contamination off with a very fine wire wool and ensuring proper washing down with fresh water during cleaning. As far as I know this resolved their issue.
    Hope that this may help somewhat.