<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2016-09-13</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001353487</issuerCik>
        <issuerName>MAGNEGAS CORP</issuerName>
        <issuerTradingSymbol>MNGA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001448450</rptOwnerCik>
            <rptOwnerName>Santilli Carla</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>11885 44TH STREET NORTH</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>CLEARWATER</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>33762</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.001 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2016-09-13</value>
                <footnoteId id="F1"/>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>129032</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.62</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3659458</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Acquired pursuant to an award under the MagneGas Corporation Amended and Restated 2014 Equity Incentive Award Plan (the &quot;Amended 2014 Plan&quot;) for her services rendered as a member of the Issuer's Board of Directors (the &quot;Board&quot;) for the period of May 15, 2015 through May 14, 2016.</footnote>
        <footnote id="F2">The Board approved the award on August 4, 2016 pursuant to Sections 9.6 and 12.1 of the Amended 2014 Plan. Pursuant to Section 9.6, the cost basis of these shares is based on the closing sales price quoted on the NASDAQ Capital Market on the 15th of the month following the date of the Board's resolutions. While the shares are being issued by the Issuer's transfer agent on September 13, 2016, the cost basis is the August 15, 2016 $0.62 closing price.</footnote>
        <footnote id="F3">As of 5:00 PM Eastern Time on September 13, 2016, the reporting person owned a total of 3,659,458 shares: (a) 1,636,719 restricted shares held by Global Alpha; (b) 186,000 restricted shares held by Global Beta; (c) 193,636 free-trading shares held by Global Beta in its brokerage account whose shares are sold pursuant to a Rule 10b5-1 trading plan; (d) 313,000 restricted shares held by Clean Energies Tech Co., a private company which is 50% owned by Ruggero Santilli; (e) 270,000 restricted shares held by the RM Santilli Foundation, a foundation which is 50% owned by the reporting person; (f) 10,000 restricted shares held in Ruggero Santilli's own name; (g) 525,000 shares of common stock underlying options held by Ruggero Santilli that are presently exercisable; (h) 225,103 shares (205,352 free-trading and 19,751 restricted) held in the name of the reporting person; and (i) 300,000 shares of common stock underlying options held by the reporting person that are presently exercisable.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Carla Santilli</signatureName>
        <signatureDate>2016-09-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
